661913988 has 12 divisors (see below), whose sum is σ = 1544466000. Its totient is φ = 220637992.

The previous prime is 661913939. The next prime is 661914013. The reversal of 661913988 is 889319166.

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

It is a self number, because there is not a number n which added to its sum of digits gives 661913988.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27579738 + ... + 27579761.

It is an arithmetic number, because the mean of its divisors is an integer number (128705500).

Almost surely, 2^661913988 is an apocalyptic number.

It is an amenable number.

661913988 is an abundant number, since it is smaller than the sum of its proper divisors (882552012).

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

661913988 is a wasteful number, since it uses less digits than its factorization.

661913988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55159506 (or 55159504 counting only the distinct ones).

The product of its digits is 559872, while the sum is 51.

The square root of 661913988 is about 25727.6891305846. The cubic root of 661913988 is about 871.4995883870.

The spelling of 661913988 in words is "six hundred sixty-one million, nine hundred thirteen thousand, nine hundred eighty-eight".