215921664 has 132 divisors (see below), whose sum is σ = 712749024. Its totient is φ = 61673472.

The previous prime is 215921659. The next prime is 215921683. The reversal of 215921664 is 466129512.

215921664 is a `hidden beast` number, since 2 + 1 + 592 + 1 + 6 + 64 = 666.

215921664 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 62839 + ... + 66185.

Almost surely, 2^215921664 is an apocalyptic number.

215921664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 215921664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (356374512).

215921664 is an abundant number, since it is smaller than the sum of its proper divisors (496827360).

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

215921664 is a wasteful number, since it uses less digits than its factorization.

215921664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3380 (or 3359 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 215921664 is about 14694.2731701844. The cubic root of 215921664 is about 599.9274578964.

The spelling of 215921664 in words is "two hundred fifteen million, nine hundred twenty-one thousand, six hundred sixty-four".