56721664 has 36 divisors (see below), whose sum is σ = 114946384. Its totient is φ = 27929088.

The previous prime is 56721659. The next prime is 56721671. The reversal of 56721664 is 46612765.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15499 + ... + 18805.

Almost surely, 2^56721664 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 56721664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (57473192).

56721664 is an abundant number, since it is smaller than the sum of its proper divisors (58224720).

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

56721664 is an equidigital number, since it uses as much as digits as its factorization.

56721664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3390 (or 3376 counting only the distinct ones).

The product of its digits is 60480, while the sum is 37.

The square root of 56721664 is about 7531.3786254576. The cubic root of 56721664 is about 384.2226717793. Note that the first 3 decimals are identical.

The spelling of 56721664 in words is "fifty-six million, seven hundred twenty-one thousand, six hundred sixty-four".