661221637576 has 32 divisors (see below), whose sum is σ = 1241540460000. Its totient is φ = 330144349696.

The previous prime is 661221637543. The next prime is 661221637589. The reversal of 661221637576 is 675736122166.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57546840 + ... + 57558328.

It is an arithmetic number, because the mean of its divisors is an integer number (38798139375).

Almost surely, 2^661221637576 is an apocalyptic number.

It is an amenable number.

661221637576 is a deficient number, since it is larger than the sum of its proper divisors (580318822424).

661221637576 is a wasteful number, since it uses less digits than its factorization.

661221637576 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21021 (or 21017 counting only the distinct ones).

The product of its digits is 3810240, while the sum is 52.

The spelling of 661221637576 in words is "six hundred sixty-one billion, two hundred twenty-one million, six hundred thirty-seven thousand, five hundred seventy-six".