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

← 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

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

In other fields

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
edit