66006666621 has 18 divisors (see below), whose sum is σ = 110909161662. Its totient is φ = 37718094960.

The previous prime is 66006666589. The next prime is 66006666623. The reversal of 66006666621 is 12666660066.

It can be written as a sum of positive squares in only one way, i.e., 66004803396 + 1863225 = 256914^2 + 1365^2 .

It is not a de Polignac number, because 66006666621 - 2⁵ = 66006666589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66006666623) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 74837050 + ... + 74837931.

Almost surely, 2^66006666621 is an apocalyptic number.

It is an amenable number.

66006666621 is a deficient number, since it is larger than the sum of its proper divisors (44902495041).

66006666621 is a wasteful number, since it uses less digits than its factorization.

66006666621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149675001 (or 149674991 counting only the distinct ones).

The product of its (nonzero) digits is 559872, while the sum is 45.

The spelling of 66006666621 in words is "sixty-six billion, six million, six hundred sixty-six thousand, six hundred twenty-one".