661312656 has 45 divisors (see below), whose sum is σ = 1851620979. Its totient is φ = 220334688.

The previous prime is 661312643. The next prime is 661312661. The reversal of 661312656 is 656213166.

The square root of 661312656 is 25716.

It is a perfect power (a square), and thus also a powerful number.

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

It is a self number, because there is not a number n which added to its sum of digits gives 661312656.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 307521 + ... + 309663.

Almost surely, 2^661312656 is an apocalyptic number.

661312656 is the 25716-th square number.

It is an amenable number.

661312656 is an abundant number, since it is smaller than the sum of its proper divisors (1190308323).

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

661312656 is an equidigital number, since it uses as much as digits as its factorization.

661312656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4300 (or 2148 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The cubic root of 661312656 is about 871.2355967009.

Multiplying 661312656 by its sum of digits (36), we get a square (23807255616 = 154296²).

661312656 divided by its sum of digits (36) gives a square (18369796 = 4286²).

The spelling of 661312656 in words is "six hundred sixty-one million, three hundred twelve thousand, six hundred fifty-six".