15665 has 8 divisors (see below), whose sum is σ = 20328. Its totient is φ = 11520.

The previous prime is 15661. The next prime is 15667. The reversal of 15665 is 56651.

15665 = T₃₈ + T₃₉ + ... + T₅₂.

15665 = 88² + 89².

15665 is nontrivially palindromic in base 3.

It can be written as a sum of positive squares in 4 ways, for example, as 1024 + 14641 = 32^2 + 121^2 .

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

It is not a de Polignac number, because 15665 - 2² = 15661 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 15665.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 56 + ... + 185.

It is an arithmetic number, because the mean of its divisors is an integer number (2541).

2¹⁵⁶⁶⁵ is an apocalyptic number.

15665 is the 89-th centered square number.

It is an amenable number.

15665 is a deficient number, since it is larger than the sum of its proper divisors (4663).

15665 is a wasteful number, since it uses less digits than its factorization.

15665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259.

The product of its digits is 900, while the sum is 23.

The square root of 15665 is about 125.1598977309. The cubic root of 15665 is about 25.0213151547.

The spelling of 15665 in words is "fifteen thousand, six hundred sixty-five".