661921993836 has 36 divisors (see below), whose sum is σ = 1673928029592. Its totient is φ = 220543567104.

The previous prime is 661921993801. The next prime is 661921993877. The reversal of 661921993836 is 638399129166.

661921993836 is a `hidden beast` number, since 6 + 61 + 9 + 2 + 199 + 383 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3962766 + ... + 4126421.

It is an arithmetic number, because the mean of its divisors is an integer number (46498000822).

Almost surely, 2^661921993836 is an apocalyptic number.

It is an amenable number.

661921993836 is an abundant number, since it is smaller than the sum of its proper divisors (1012006035756).

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

661921993836 is a wasteful number, since it uses less digits than its factorization.

661921993836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8091470 (or 8091465 counting only the distinct ones).

The product of its digits is 22674816, while the sum is 63.

The spelling of 661921993836 in words is "six hundred sixty-one billion, nine hundred twenty-one million, nine hundred ninety-three thousand, eight hundred thirty-six".