15865 has 8 divisors (see below), whose sum is σ = 20160. Its totient is φ = 11952.

The previous prime is 15859. The next prime is 15877. The reversal of 15865 is 56851.

15865 = T₃₁ + T₃₂ + ... + T₄₉.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 15865 - 2⁷ = 15737 is a prime.

It is a plaindrome in base 9.

It is a nialpdrome in base 12.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12 + ... + 178.

It is an arithmetic number, because the mean of its divisors is an integer number (2520).

2¹⁵⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

15865 is a deficient number, since it is larger than the sum of its proper divisors (4295).

15865 is a wasteful number, since it uses less digits than its factorization.

15865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191.

The product of its digits is 1200, while the sum is 25.

The square root of 15865 is about 125.9563416427. The cubic root of 15865 is about 25.1273501758.

The spelling of 15865 in words is "fifteen thousand, eight hundred sixty-five".