639637 has 2 divisors, whose sum is σ = 639638. Its totient is φ = 639636.

The previous prime is 639631. The next prime is 639647. The reversal of 639637 is 736936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 579121 + 60516 = 761^2 + 246^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319818 + 319819.

It is an arithmetic number, because the mean of its divisors is an integer number (319819).

2⁶³⁹⁶³⁷ is an apocalyptic number.

It is an amenable number.

639637 is a deficient number, since it is larger than the sum of its proper divisors (1).

639637 is an equidigital number, since it uses as much as digits as its factorization.

639637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20412, while the sum is 34.

The square root of 639637 is about 799.7730928207. The cubic root of 639637 is about 86.1610916076.

The spelling of 639637 in words is "six hundred thirty-nine thousand, six hundred thirty-seven".