151
E151 is Brilliant Black BN.
- Odd
- Prime
Where 151 fits
Why 151 is special
It is one of the colours restricted or avoided in several jurisdictions, and it is banned outright in some, which is why product formulations differ by market.
151 is part of
Factors & digit properties
- Divisors (2)
- 1, 151
- Prime factorisation
- 151
- Digit sum
- 7
- Digital root
- 7
Representations
- Decimal
- 151
- Scientific notation
- 1.510 × 10^2
Roman numerals
C L I
Binary
1 0 0 1 0 1 1 1
1 × 128 + 0 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 1 × 4 + 1 × 2 + 1 × 1 = 151
Octal
2 2 7
2 × 64 + 2 × 8 + 7 × 1 = 151
Hexadecimal
9 7
9 × 16 + 7 × 1 = 151
Read as powers of two: 128 + 16 + 4 + 2 + 1 = 151.
In historical numeral systems
Egyptian
1 coil of rope, 5 hobbles, 1 stroke
1 × 100 + 5 × 10 + 1 × 1 = 151. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 vertical wedges (sixties place), 3 corner wedges + 1 vertical wedge (units place)
2 × 60 + 31 = 151. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
rho, then nu, then alpha, marked as a numeral
rho-nu-alpha + keraia
rho + 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
qof, then nun, then alef
qof-nun-alef
qof (100) + nun (50) + alef (1) = 151, written in descending order.
Maya
1 bar + 2 dots (upper, twenties place) over 2 bars + 1 dot (lower, units place)
7 × 20 + 11 = 151. 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
- Palindromic number
- Deficient number
- Lucky number (mathematical sieve)
- Twin prime
Related numbers & connections
Both are synthetic dyes subject to differing national restrictions, which is why formulations vary by market.
View 132 →Everyday life
E151 Brilliant Black BN is a synthetic azo dye permitted in the European Union and prohibited in several other jurisdictions, producing market-specific formulations.
DocumentedEveryday lifeGeography: European Union and states adopting the E number systemPeriod: 1962–
Common questions
Is 151 a prime number?
Yes, 151 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 151?
The factors of 151 are 1, 151.
What is 151 in Roman numerals?
151 in Roman numerals is CLI.
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