253657721 has 2 divisors, whose sum is σ = 253657722. Its totient is φ = 253657720.

The previous prime is 253657709. The next prime is 253657727. The reversal of 253657721 is 127756352.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 149719696 + 103938025 = 12236^2 + 10195^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-253657721 is a prime.

It is not a weakly prime, because it can be changed into another prime (253657727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 126828860 + 126828861.

It is an arithmetic number, because the mean of its divisors is an integer number (126828861).

Almost surely, 2^253657721 is an apocalyptic number.

It is an amenable number.

253657721 is a deficient number, since it is larger than the sum of its proper divisors (1).

253657721 is an equidigital number, since it uses as much as digits as its factorization.

253657721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 88200, while the sum is 38.

The square root of 253657721 is about 15926.6355831984. The cubic root of 253657721 is about 633.0179552286.

The spelling of 253657721 in words is "two hundred fifty-three million, six hundred fifty-seven thousand, seven hundred twenty-one".