639907 has 2 divisors, whose sum is σ = 639908. Its totient is φ = 639906.

The previous prime is 639857. The next prime is 639911. The reversal of 639907 is 709936.

639907 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639907 is a prime.

It is not a weakly prime, because it can be changed into another prime (639937) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319953 + 319954.

It is an arithmetic number, because the mean of its divisors is an integer number (319954).

2⁶³⁹⁹⁰⁷ is an apocalyptic number.

639907 is a deficient number, since it is larger than the sum of its proper divisors (1).

639907 is an equidigital number, since it uses as much as digits as its factorization.

639907 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10206, while the sum is 34.

The square root of 639907 is about 799.9418728883. The cubic root of 639907 is about 86.1732131819.

The spelling of 639907 in words is "six hundred thirty-nine thousand, nine hundred seven".