639765257 has 2 divisors, whose sum is σ = 639765258. Its totient is φ = 639765256.

The previous prime is 639765251. The next prime is 639765277. The reversal of 639765257 is 752567936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 631818496 + 7946761 = 25136^2 + 2819^2 .

It is a cyclic number.

It is not a de Polignac number, because 639765257 - 2⁶ = 639765193 is a prime.

It is not a weakly prime, because it can be changed into another prime (639765251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319882628 + 319882629.

It is an arithmetic number, because the mean of its divisors is an integer number (319882629).

Almost surely, 2^639765257 is an apocalyptic number.

It is an amenable number.

639765257 is a deficient number, since it is larger than the sum of its proper divisors (1).

639765257 is an equidigital number, since it uses as much as digits as its factorization.

639765257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2381400, while the sum is 50.

The square root of 639765257 is about 25293.5813399368. The cubic root of 639765257 is about 861.6685009487.

The spelling of 639765257 in words is "six hundred thirty-nine million, seven hundred sixty-five thousand, two hundred fifty-seven".