61
Roger Maris hit 61 home runs in 1961, breaking a record that had stood since 1927. 61 is prime, and the atomic number of promethium — the only lanthanide with no stable isotope.
- Odd
- Prime
Where 61 fits
Why 61 is special
61 is the mirror image of 59 across 60: the first prime after it, just as 59 is the last prime before it — and, in baseball, the number Roger Maris reached in 1961 to break Babe Ruth's single-season home run record.
Same number, different meanings
How 61 is understood across different contexts — never implying one meaning because of another.
- Mathematics
61 is the mirror image of 59 across 60: the first prime after it, just as 59 is the last prime before it — and, in baseball, the number Roger Maris reached in 1961 to break Babe Ruth's single-season home run record.
- Geography
+61 reaches Australia, in the 6x block covering Oceania and South-East Asia. Australia's emergency number 000 cannot be dialled from outside the country regardless of the code — international callers reach 112 on a mobile instead.
- Sport
New York Yankees outfielder Roger Maris hit 61 home runs during the 1961 Major League Baseball season, breaking Babe Ruth's 34-year-old single-season record of 60.
- Science
61 is the atomic number of promethium, the only lanthanide with no stable isotope. It is essentially absent from Earth's crust and has to be made in reactors.
61 is part of
Factors & digit properties
- Divisors (2)
- 1, 61
- Prime factorisation
- 61
- Digit sum
- 7
- Digital root
- 7
Representations
- Decimal
- 61
- Scientific notation
- 6.100 × 10^1
Roman numerals
L X I
Binary
1 1 1 1 0 1
1 × 32 + 1 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 61
Octal
7 5
7 × 8 + 5 × 1 = 61
Hexadecimal
3 d
3 × 16 + d × 1 = 61
Read as powers of two: 32 + 16 + 8 + 4 + 1 = 61.
In historical numeral systems
Egyptian
6 hobbles, 1 stroke
6 × 10 + 1 × 1 = 61. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 vertical wedge (sixties place), 1 vertical wedge (units place)
1 × 60 + 1 = 61. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
xi, then alpha, marked as a numeral
xi-alpha + keraia
xi + alpha written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
samekh, then alef
samekh-alef
samekh (60) + alef (1) = 61, written in descending order.
Chinese numerals
liù shí yī
liù shí yī
六 before 十 multiplies it: 6 tens. 一 after it adds 1. The written form mirrors the arithmetic — "liù shí yī". The financial (anti-fraud) form is 陸拾壹.
Maya
3 dots (upper, twenties place) over 1 dot (lower, units place)
3 × 20 + 1 = 61. Places stack vertically with the smallest at the bottom, so the upper group is worth twenty times the lower.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Deficient number
- Twin prime
Related numbers & connections
59 and 61 are twin primes — two primes exactly two apart.
View 59 →Roger Maris's 61 home runs in the 1961 season broke the previous single-season record of 60.
Norfolk Island and Australia's Antarctic territory share +672 and are both Australian administrations, which is a bureaucratic pairing rather than a geographic one.
View 672 →Geography
+61 reaches Australia, in the 6x block covering Oceania and South-East Asia. Australia's emergency number 000 cannot be dialled from outside the country regardless of the code — international callers reach 112 on a mobile instead.
DocumentedGeographyGeography: Australia
Sport
New York Yankees outfielder Roger Maris hit 61 home runs during the 1961 Major League Baseball season, breaking Babe Ruth's 34-year-old single-season record of 60.
DocumentedSportGeography: United States (MLB)Period: 1961
Science
61 is the atomic number of promethium, the only lanthanide with no stable isotope. It is essentially absent from Earth's crust and has to be made in reactors.
DocumentedScience
Mathematics
61 is prime, sitting directly after the highly composite number 60.
DocumentedMathematics
Common questions
Who hit 61 home runs?
Roger Maris, for the New York Yankees, in 1961 — breaking Babe Ruth's single-season record of 60, set in 1927. The record stood until 1998. Maris played a 162-game season where Ruth had played 154, and the commissioner's insistence on noting that difference became one of baseball's longest-running arguments.
Is 61 a prime number?
Yes, 61 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 61?
The factors of 61 are 1, 61.
What is 61 in Roman numerals?
61 in Roman numerals is LXI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 4 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026