951
951 Gaspra was the first asteroid photographed close up.
- Odd
- Composite
Where 951 fits
Why 951 is special
Galileo passed it in 1991 on the way to Jupiter, and the images ended centuries of asteroids being nothing but moving points of light.
Factors & digit properties
- Divisors (4)
- 1, 3, 317, 951
- Prime factorisation
- 3 × 317
- Digit sum
- 15
- Digital root
- 6
Representations
- Decimal
- 951
- Scientific notation
- 9.510 × 10^2
Roman numerals
C M L I
CMLI uses the subtractive pair CM: a hundred before a thousand — a thousand minus a hundred.
Binary
1 1 1 0 1 1 0 1 1 1
1 × 512 + 1 × 256 + 1 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 0 × 8 + 1 × 4 + 1 × 2 + 1 × 1 = 951
Octal
1 6 6 7
1 × 512 + 6 × 64 + 6 × 8 + 7 × 1 = 951
Hexadecimal
3 b 7
3 × 256 + b × 16 + 7 × 1 = 951
Read as powers of two: 512 + 256 + 128 + 32 + 16 + 4 + 2 + 1 = 951.
In historical numeral systems
Egyptian
9 coils of rope, 5 hobbles, 1 stroke
9 × 100 + 5 × 10 + 1 × 1 = 951. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 corner wedge + 5 vertical wedges (sixties place), 5 corner wedges + 1 vertical wedge (units place)
15 × 60 + 51 = 951. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
sampi, then nu, then alpha, marked as a numeral
sampi-nu-alpha + keraia
sampi + nu + alpha written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
tav, then tav, then qof, then nun, then alef
tav-tav-qof-nun-alef
tav (400) + tav (400) + qof (100) + nun (50) + alef (1) = 951, written in descending order.
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
- Semiprime
Related numbers & connections
Gaspra was the first asteroid photographed close up, six years before Eros became the first orbited and landed on.
View 433 →Science
The Galileo spacecraft flew past 951 Gaspra in October 1991, returning the first close-range images of an asteroid and showing an irregular, heavily cratered body.
DocumentedSciencePeriod: 1916–
Common questions
Is 951 a prime number?
No, 951 is not prime.
What are the factors of 951?
The factors of 951 are 1, 3, 317, 951.
What is 951 in Roman numerals?
951 in Roman numerals is CMLI. CM is subtractive: a hundred before a thousand — a thousand minus a hundred. Written additively it would be DCCCCLI, which Roman inscriptions used freely — the strict subtractive form is a later convention.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 15 July 2026