639258749 has 2 divisors, whose sum is σ = 639258750. Its totient is φ = 639258748.

The previous prime is 639258733. The next prime is 639258751. The reversal of 639258749 is 947852936.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 520296100 + 118962649 = 22810^2 + 10907^2 .

It is a cyclic number.

It is not a de Polignac number, because 639258749 - 2⁴ = 639258733 is a prime.

Together with 639258751, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 639258749.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639258449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319629374 + 319629375.

It is an arithmetic number, because the mean of its divisors is an integer number (319629375).

Almost surely, 2^639258749 is an apocalyptic number.

It is an amenable number.

639258749 is a deficient number, since it is larger than the sum of its proper divisors (1).

639258749 is an equidigital number, since it uses as much as digits as its factorization.

639258749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3265920, while the sum is 53.

The square root of 639258749 is about 25283.5667776522. The cubic root of 639258749 is about 861.4410439695.

The spelling of 639258749 in words is "six hundred thirty-nine million, two hundred fifty-eight thousand, seven hundred forty-nine".