661621656 has 16 divisors (see below), whose sum is σ = 1654054200. Its totient is φ = 220540544.

The previous prime is 661621627. The next prime is 661621661. The reversal of 661621656 is 656126166.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13783761 + ... + 13783808.

Almost surely, 2^661621656 is an apocalyptic number.

It is an amenable number.

661621656 is an abundant number, since it is smaller than the sum of its proper divisors (992432544).

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

661621656 is a wasteful number, since it uses less digits than its factorization.

661621656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27567578 (or 27567574 counting only the distinct ones).

The product of its digits is 77760, while the sum is 39.

The square root of 661621656 is about 25722.0072311630. The cubic root of 661621656 is about 871.3712712455.

The spelling of 661621656 in words is "six hundred sixty-one million, six hundred twenty-one thousand, six hundred fifty-six".