639959 has 2 divisors, whose sum is σ = 639960. Its totient is φ = 639958.

The previous prime is 639949. The next prime is 639983. The reversal of 639959 is 959936.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 639959 - 2⁸ = 639703 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319979 + 319980.

It is an arithmetic number, because the mean of its divisors is an integer number (319980).

2⁶³⁹⁹⁵⁹ is an apocalyptic number.

639959 is a deficient number, since it is larger than the sum of its proper divisors (1).

639959 is an equidigital number, since it uses as much as digits as its factorization.

639959 is an evil number, because the sum of its binary digits is even.

The product of its digits is 65610, while the sum is 41.

The square root of 639959 is about 799.9743745896. The cubic root of 639959 is about 86.1755473157.

Adding to 639959 its sum of digits (41), we get a square (640000 = 800²).

The spelling of 639959 in words is "six hundred thirty-nine thousand, nine hundred fifty-nine".