639696257 has 8 divisors (see below), whose sum is σ = 647994600. Its totient is φ = 631442304.

The previous prime is 639696241. The next prime is 639696269. The reversal of 639696257 is 752696936.

It can be written as a sum of positive squares in 4 ways, for example, as 63744256 + 575952001 = 7984^2 + 23999^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639696257 - 2⁴ = 639696241 is a prime.

It is a super-2 number, since 2×639696257² = 818422602439620098, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639696199 and 639696208.

It is not an unprimeable number, because it can be changed into a prime (639696857) 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 in 7 ways as a sum of consecutive naturals, for example, 18413 + ... + 40229.

It is an arithmetic number, because the mean of its divisors is an integer number (80999325).

Almost surely, 2^639696257 is an apocalyptic number.

It is an amenable number.

639696257 is a deficient number, since it is larger than the sum of its proper divisors (8298343).

639696257 is a wasteful number, since it uses less digits than its factorization.

639696257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22195.

The product of its digits is 3674160, while the sum is 53.

The square root of 639696257 is about 25292.2173207491. The cubic root of 639696257 is about 861.6375222610.

The spelling of 639696257 in words is "six hundred thirty-nine million, six hundred ninety-six thousand, two hundred fifty-seven".