639831749 has 2 divisors, whose sum is σ = 639831750. Its totient is φ = 639831748.

The previous prime is 639831743. The next prime is 639831791. The reversal of 639831749 is 947138936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 525234724 + 114597025 = 22918^2 + 10705^2 .

It is a cyclic number.

It is not a de Polignac number, because 639831749 - 2¹⁶ = 639766213 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 639831697 and 639831706.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639831743) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319915874 + 319915875.

It is an arithmetic number, because the mean of its divisors is an integer number (319915875).

Almost surely, 2^639831749 is an apocalyptic number.

It is an amenable number.

639831749 is a deficient number, since it is larger than the sum of its proper divisors (1).

639831749 is an equidigital number, since it uses as much as digits as its factorization.

639831749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 979776, while the sum is 50.

The square root of 639831749 is about 25294.8957103998. The cubic root of 639831749 is about 861.6983515210.

The spelling of 639831749 in words is "six hundred thirty-nine million, eight hundred thirty-one thousand, seven hundred forty-nine".