639857 has 2 divisors, whose sum is σ = 639858. Its totient is φ = 639856.

The previous prime is 639853. The next prime is 639907. The reversal of 639857 is 758936.

639857 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 633616 + 6241 = 796^2 + 79^2 .

It is a cyclic number.

It is not a de Polignac number, because 639857 - 2² = 639853 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 639857.

It is not a weakly prime, because it can be changed into another prime (639851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319928 + 319929.

It is an arithmetic number, because the mean of its divisors is an integer number (319929).

2⁶³⁹⁸⁵⁷ is an apocalyptic number.

It is an amenable number.

639857 is a deficient number, since it is larger than the sum of its proper divisors (1).

639857 is an equidigital number, since it uses as much as digits as its factorization.

639857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45360, while the sum is 38.

The square root of 639857 is about 799.9106200070. The cubic root of 639857 is about 86.1709687032.

The spelling of 639857 in words is "six hundred thirty-nine thousand, eight hundred fifty-seven".