315745721 has 2 divisors, whose sum is σ = 315745722. Its totient is φ = 315745720.

The previous prime is 315745711. The next prime is 315745723. The reversal of 315745721 is 127547513.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 307125625 + 8620096 = 17525^2 + 2936^2 .

It is a cyclic number.

It is not a de Polignac number, because 315745721 - 2⁶ = 315745657 is a prime.

Together with 315745723, 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 (315745723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 157872860 + 157872861.

It is an arithmetic number, because the mean of its divisors is an integer number (157872861).

Almost surely, 2^315745721 is an apocalyptic number.

It is an amenable number.

315745721 is a deficient number, since it is larger than the sum of its proper divisors (1).

315745721 is an equidigital number, since it uses as much as digits as its factorization.

315745721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 29400, while the sum is 35.

The square root of 315745721 is about 17769.2352395932. The cubic root of 315745721 is about 680.9457148400.

The spelling of 315745721 in words is "three hundred fifteen million, seven hundred forty-five thousand, seven hundred twenty-one".