15921 has 12 divisors (see below), whose sum is σ = 24180. Its totient is φ = 10080.

The previous prime is 15919. The next prime is 15923. The reversal of 15921 is 12951.

15921 = 10² + 11² + ... + 36².

15921 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (15919) and next prime (15923).

It can be written as a sum of positive squares in 2 ways, for example, as 3600 + 12321 = 60^2 + 111^2 .

It is not a de Polignac number, because 15921 - 2¹ = 15919 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 15894 and 15903.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 15921.

It is not an unprimeable number, because it can be changed into a prime (15923) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 231 + ... + 291.

It is an arithmetic number, because the mean of its divisors is an integer number (2015).

2¹⁵⁹²¹ is an apocalyptic number.

It is an amenable number.

15921 is a deficient number, since it is larger than the sum of its proper divisors (8259).

15921 is a wasteful number, since it uses less digits than its factorization.

15921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96 (or 93 counting only the distinct ones).

The product of its digits is 90, while the sum is 18.

The square root of 15921 is about 126.1784450689. The cubic root of 15921 is about 25.1568801522.

The spelling of 15921 in words is "fifteen thousand, nine hundred twenty-one".