66210925681 has 2 divisors, whose sum is σ = 66210925682. Its totient is φ = 66210925680.

The previous prime is 66210925673. The next prime is 66210925687. The reversal of 66210925681 is 18652901266.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47060794225 + 19150131456 = 216935^2 + 138384^2 .

It is a cyclic number.

It is not a de Polignac number, because 66210925681 - 2³ = 66210925673 is a prime.

It is a super-2 number, since 2×66210925681² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (66210925687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33105462840 + 33105462841.

It is an arithmetic number, because the mean of its divisors is an integer number (33105462841).

Almost surely, 2^66210925681 is an apocalyptic number.

It is an amenable number.

66210925681 is a deficient number, since it is larger than the sum of its proper divisors (1).

66210925681 is an equidigital number, since it uses as much as digits as its factorization.

66210925681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 311040, while the sum is 46.

The spelling of 66210925681 in words is "sixty-six billion, two hundred ten million, nine hundred twenty-five thousand, six hundred eighty-one".