64660721 has 2 divisors, whose sum is σ = 64660722. Its totient is φ = 64660720.

The previous prime is 64660711. The next prime is 64660753. The reversal of 64660721 is 12706646.

It is an a-pointer prime, because the next prime (64660753) can be obtained adding 64660721 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54169600 + 10491121 = 7360^2 + 3239^2 .

It is a cyclic number.

It is not a de Polignac number, because 64660721 - 2⁶ = 64660657 is a prime.

It is not a weakly prime, because it can be changed into another prime (64660711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32330360 + 32330361.

It is an arithmetic number, because the mean of its divisors is an integer number (32330361).

Almost surely, 2^64660721 is an apocalyptic number.

It is an amenable number.

64660721 is a deficient number, since it is larger than the sum of its proper divisors (1).

64660721 is an equidigital number, since it uses as much as digits as its factorization.

64660721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 32.

The square root of 64660721 is about 8041.1890289932. The cubic root of 64660721 is about 401.3717921709.

The spelling of 64660721 in words is "sixty-four million, six hundred sixty thousand, seven hundred twenty-one".