661564990 has 24 divisors (see below), whose sum is σ = 1256797080. Its totient is φ = 250696944.

The previous prime is 661564987. The next prime is 661564999. The reversal of 661564990 is 99465166.

It is a self number, because there is not a number n which added to its sum of digits gives 661564990.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661564999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 88020 + ... + 95239.

It is an arithmetic number, because the mean of its divisors is an integer number (52366545).

Almost surely, 2^661564990 is an apocalyptic number.

661564990 is a deficient number, since it is larger than the sum of its proper divisors (595232090).

661564990 is a wasteful number, since it uses less digits than its factorization.

661564990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 183304 (or 183285 counting only the distinct ones).

The product of its (nonzero) digits is 349920, while the sum is 46.

The square root of 661564990 is about 25720.9056994500. The cubic root of 661564990 is about 871.3463937173.

The spelling of 661564990 in words is "six hundred sixty-one million, five hundred sixty-four thousand, nine hundred ninety".