661886613621 has 32 divisors (see below), whose sum is σ = 1032250044800. Its totient is φ = 418006033920.

The previous prime is 661886613601. The next prime is 661886613671. The reversal of 661886613621 is 126316688166.

661886613621 is a `hidden beast` number, since 6 + 6 + 1 + 8 + 8 + 6 + 6 + 1 + 3 + 621 = 666.

It is not a de Polignac number, because 661886613621 - 2¹⁴ = 661886597237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661886613601) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10063575 + ... + 10129131.

It is an arithmetic number, because the mean of its divisors is an integer number (32257813900).

Almost surely, 2^661886613621 is an apocalyptic number.

It is an amenable number.

661886613621 is a deficient number, since it is larger than the sum of its proper divisors (370363431179).

661886613621 is a wasteful number, since it uses less digits than its factorization.

661886613621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85266 (or 85260 counting only the distinct ones).

The product of its digits is 2985984, while the sum is 54.

The spelling of 661886613621 in words is "six hundred sixty-one billion, eight hundred eighty-six million, six hundred thirteen thousand, six hundred twenty-one".