639681577 has 2 divisors, whose sum is σ = 639681578. Its totient is φ = 639681576.

The previous prime is 639681551. The next prime is 639681613. The reversal of 639681577 is 775186936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 612859536 + 26822041 = 24756^2 + 5179^2 .

It is a cyclic number.

It is not a de Polignac number, because 639681577 - 2¹⁵ = 639648809 is a prime.

It is a super-4 number, since 4×639681577⁴ (a number of 36 digits) contains 4444 as substring.

It is not a weakly prime, because it can be changed into another prime (639681527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319840788 + 319840789.

It is an arithmetic number, because the mean of its divisors is an integer number (319840789).

Almost surely, 2^639681577 is an apocalyptic number.

It is an amenable number.

639681577 is a deficient number, since it is larger than the sum of its proper divisors (1).

639681577 is an equidigital number, since it uses as much as digits as its factorization.

639681577 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1905120, while the sum is 52.

The square root of 639681577 is about 25291.9271112345. The cubic root of 639681577 is about 861.6309311456.

The spelling of 639681577 in words is "six hundred thirty-nine million, six hundred eighty-one thousand, five hundred seventy-seven".