15 (number)

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← 14 15 16 →
Cardinalfifteen
Ordinal15th
(fifteenth)
Numeral systempentadecimal
Factorization3 × 5
Divisors1, 3, 5, 15
Greek numeralΙΕ´
Roman numeralXV
Binary11112
Ternary1203
Senary236
Octal178
Duodecimal1312
HexadecimalF16
Hebrew numeralט"ו / י"ה
Babylonian numeral𒌋𒐙

15 (fifteen) is the natural number following 14 and preceding 16.

Mathematics[edit]

M = 15
The 15 perfect matchings of K6
15 as the difference of two positive squares (in orange).

15 is:

Furthermore,

2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397 (sequence A020994 in the OEIS)

Science[edit]

Seashells from the mollusk Donax variabilis have 15 coloring pattern phenotypes.

Religion[edit]

Sunnism[edit]

The Hanbali Sunni madhab states that the age of fifteen of a solar or lunar calendar is when one's taklif (obligation or responsibility) begins and is the stage whereby one has his deeds recorded.[9]

Judaism[edit]

References[edit]

  1. ^ Sloane, N. J. A. (ed.). "Sequence A001358 (Semiprimes (or biprimes): products of two primes.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  2. ^ Sloane, N. J. A. (ed.). "Sequence A001748 (a(n) = 3 * prime(n))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  3. ^ Sloane, N. J. A. (ed.). "Sequence A000110 (Bell or exponential numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  4. ^ Sloane, N. J. A. (ed.). "Sequence A000332 (Binomial coefficient binomial(n,4) = n*(n-1)*(n-2)*(n-3)/24)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  5. ^ Sloane, N. J. A. (ed.). "Sequence A000384 (Hexagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  6. ^ Sloane, N. J. A. (ed.). "Sequence A051867 (pentadecagonal numbers.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  7. ^ Sloane, N. J. A. (ed.). "Sequence A334078 (a(n) is the smallest positive integer that can be expressed as the difference of two positive squares in at least n ways.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  8. ^ H.S.M. Coxeter (1954). "Regular Honeycombs in Hyperbolic Space". Proceedings of the International Congress of Mathematicians. 3: 155–169. CiteSeerX 10.1.1.361.251.
  9. ^ Spevack, Aaron (2011). Ghazali on the Principles of Islamic Spiritualit. p. 50.

Further reading[edit]

External links[edit]