66604625981 has 2 divisors, whose sum is σ = 66604625982. Its totient is φ = 66604625980.

The previous prime is 66604625957. The next prime is 66604626007. The reversal of 66604625981 is 18952640666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51508572025 + 15096053956 = 226955^2 + 122866^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66604625981 is a prime.

It is a super-2 number, since 2×66604625981² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66604625921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33302312990 + 33302312991.

It is an arithmetic number, because the mean of its divisors is an integer number (33302312991).

Almost surely, 2^66604625981 is an apocalyptic number.

It is an amenable number.

66604625981 is a deficient number, since it is larger than the sum of its proper divisors (1).

66604625981 is an equidigital number, since it uses as much as digits as its factorization.

66604625981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3732480, while the sum is 53.

The spelling of 66604625981 in words is "sixty-six billion, six hundred four million, six hundred twenty-five thousand, nine hundred eighty-one".