642915857 has 2 divisors, whose sum is σ = 642915858. Its totient is φ = 642915856.

The previous prime is 642915733. The next prime is 642915883. The reversal of 642915857 is 758519246.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 359633296 + 283282561 = 18964^2 + 16831^2 .

It is a cyclic number.

It is not a de Polignac number, because 642915857 - 2²² = 638721553 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (642915887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321457928 + 321457929.

It is an arithmetic number, because the mean of its divisors is an integer number (321457929).

Almost surely, 2^642915857 is an apocalyptic number.

It is an amenable number.

642915857 is a deficient number, since it is larger than the sum of its proper divisors (1).

642915857 is an equidigital number, since it uses as much as digits as its factorization.

642915857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 604800, while the sum is 47.

The square root of 642915857 is about 25355.7854739308. The cubic root of 642915857 is about 863.0806483443.

The spelling of 642915857 in words is "six hundred forty-two million, nine hundred fifteen thousand, eight hundred fifty-seven".