66760721 has 2 divisors, whose sum is σ = 66760722. Its totient is φ = 66760720.

The previous prime is 66760703. The next prime is 66760723. The reversal of 66760721 is 12706766.

66760721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58140625 + 8620096 = 7625^2 + 2936^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66760721 is a prime.

Together with 66760723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (66760723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33380360 + 33380361.

It is an arithmetic number, because the mean of its divisors is an integer number (33380361).

Almost surely, 2^66760721 is an apocalyptic number.

It is an amenable number.

66760721 is a deficient number, since it is larger than the sum of its proper divisors (1).

66760721 is an equidigital number, since it uses as much as digits as its factorization.

66760721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21168, while the sum is 35.

The square root of 66760721 is about 8170.7234073857. The cubic root of 66760721 is about 405.6707292523.

The spelling of 66760721 in words is "sixty-six million, seven hundred sixty thousand, seven hundred twenty-one".