639665249 has 2 divisors, whose sum is σ = 639665250. Its totient is φ = 639665248.

The previous prime is 639665233. The next prime is 639665261. The reversal of 639665249 is 942566936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 584430625 + 55234624 = 24175^2 + 7432^2 .

It is a cyclic number.

It is not a de Polignac number, because 639665249 - 2⁴ = 639665233 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 639665197 and 639665206.

It is not a weakly prime, because it can be changed into another prime (639665849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319832624 + 319832625.

It is an arithmetic number, because the mean of its divisors is an integer number (319832625).

Almost surely, 2^639665249 is an apocalyptic number.

It is an amenable number.

639665249 is a deficient number, since it is larger than the sum of its proper divisors (1).

639665249 is an equidigital number, since it uses as much as digits as its factorization.

639665249 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2099520, while the sum is 50.

The square root of 639665249 is about 25291.6043184295. The cubic root of 639665249 is about 861.6235999827.

The spelling of 639665249 in words is "six hundred thirty-nine million, six hundred sixty-five thousand, two hundred forty-nine".