721646257 has 2 divisors, whose sum is σ = 721646258. Its totient is φ = 721646256.

The previous prime is 721646249. The next prime is 721646269. The reversal of 721646257 is 752646127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 636250176 + 85396081 = 25224^2 + 9241^2 .

It is a cyclic number.

It is not a de Polignac number, because 721646257 - 2³ = 721646249 is a prime.

It is a super-2 number, since 2×721646257² = 1041546640484220098, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (721646857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360823128 + 360823129.

It is an arithmetic number, because the mean of its divisors is an integer number (360823129).

Almost surely, 2^721646257 is an apocalyptic number.

It is an amenable number.

721646257 is a deficient number, since it is larger than the sum of its proper divisors (1).

721646257 is an equidigital number, since it uses as much as digits as its factorization.

721646257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 40.

The square root of 721646257 is about 26863.4744029882. The cubic root of 721646257 is about 896.9635352583.

The spelling of 721646257 in words is "seven hundred twenty-one million, six hundred forty-six thousand, two hundred fifty-seven".