639891247 has 2 divisors, whose sum is σ = 639891248. Its totient is φ = 639891246.

The previous prime is 639891179. The next prime is 639891319. The reversal of 639891247 is 742198936.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639891247 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 639891247.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639891047) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319945623 + 319945624.

It is an arithmetic number, because the mean of its divisors is an integer number (319945624).

Almost surely, 2^639891247 is an apocalyptic number.

639891247 is a deficient number, since it is larger than the sum of its proper divisors (1).

639891247 is an equidigital number, since it uses as much as digits as its factorization.

639891247 is an evil number, because the sum of its binary digits is even.

The product of its digits is 653184, while the sum is 49.

The square root of 639891247 is about 25296.0717701385. The cubic root of 639891247 is about 861.7250604902.

The spelling of 639891247 in words is "six hundred thirty-nine million, eight hundred ninety-one thousand, two hundred forty-seven".