66600531621 has 12 divisors (see below), whose sum is σ = 103600827148. Its totient is φ = 40984942464.

The previous prime is 66600531617. The next prime is 66600531623. The reversal of 66600531621 is 12613500666.

It can be written as a sum of positive squares in 2 ways, for example, as 15213989025 + 51386542596 = 123345^2 + 226686^2 .

It is not a de Polignac number, because 66600531621 - 2² = 66600531617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66600531623) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 284617540 + ... + 284617773.

Almost surely, 2^66600531621 is an apocalyptic number.

It is an amenable number.

66600531621 is a deficient number, since it is larger than the sum of its proper divisors (37000295527).

66600531621 is a wasteful number, since it uses less digits than its factorization.

66600531621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 569235332 (or 569235329 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 36.

The spelling of 66600531621 in words is "sixty-six billion, six hundred million, five hundred thirty-one thousand, six hundred twenty-one".