66733666721 has 2 divisors, whose sum is σ = 66733666722. Its totient is φ = 66733666720.

The previous prime is 66733666717. The next prime is 66733666819. The reversal of 66733666721 is 12766633766.

It is a happy number.

66733666721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 52276249600 + 14457417121 = 228640^2 + 120239^2 .

It is a cyclic number.

It is not a de Polignac number, because 66733666721 - 2² = 66733666717 is a prime.

It is not a weakly prime, because it can be changed into another prime (66733696721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33366833360 + 33366833361.

It is an arithmetic number, because the mean of its divisors is an integer number (33366833361).

Almost surely, 2^66733666721 is an apocalyptic number.

It is an amenable number.

66733666721 is a deficient number, since it is larger than the sum of its proper divisors (1).

66733666721 is an equidigital number, since it uses as much as digits as its factorization.

66733666721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6858432, while the sum is 53.

The spelling of 66733666721 in words is "sixty-six billion, seven hundred thirty-three million, six hundred sixty-six thousand, seven hundred twenty-one".