15921664 has 60 divisors (see below), whose sum is σ = 35103222. Its totient is φ = 7208960.

The previous prime is 15921643. The next prime is 15921701. The reversal of 15921664 is 46612951.

It can be written as a sum of positive squares in only one way, i.e., 8952064 + 6969600 = 2992^2 + 2640^2 .

Its product of digits (12960) is a multiple of the sum of its prime divisors (270).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 61824 + ... + 62080.

Almost surely, 2^15921664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 15921664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (17551611).

15921664 is an abundant number, since it is smaller than the sum of its proper divisors (19181558).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

15921664 is an equidigital number, since it uses as much as digits as its factorization.

15921664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297 (or 270 counting only the distinct ones).

The product of its digits is 12960, while the sum is 34.

The square root of 15921664 is about 3990.1959851616. The cubic root of 15921664 is about 251.5722987760.

The spelling of 15921664 in words is "fifteen million, nine hundred twenty-one thousand, six hundred sixty-four".