661957788 has 12 divisors (see below), whose sum is σ = 1544568200. Its totient is φ = 220652592.

The previous prime is 661957771. The next prime is 661957817. The reversal of 661957788 is 887759166.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-2 number, since 2×661957788² = 876376226187705888, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27581563 + ... + 27581586.

Almost surely, 2^661957788 is an apocalyptic number.

It is an amenable number.

661957788 is an abundant number, since it is smaller than the sum of its proper divisors (882610412).

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

661957788 is a wasteful number, since it uses less digits than its factorization.

661957788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55163156 (or 55163154 counting only the distinct ones).

The product of its digits is 5080320, while the sum is 57.

The square root of 661957788 is about 25728.5403394751. The cubic root of 661957788 is about 871.5188108442.

The spelling of 661957788 in words is "six hundred sixty-one million, nine hundred fifty-seven thousand, seven hundred eighty-eight".