639832681 has 4 divisors (see below), whose sum is σ = 639948672. Its totient is φ = 639716692.

The previous prime is 639832649. The next prime is 639832691. The reversal of 639832681 is 186238936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 639832681 - 2⁵ = 639832649 is a prime.

It is a super-2 number, since 2×639832681² = 818771719351295522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639832631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 49285 + ... + 60898.

It is an arithmetic number, because the mean of its divisors is an integer number (159987168).

Almost surely, 2^639832681 is an apocalyptic number.

It is an amenable number.

639832681 is a deficient number, since it is larger than the sum of its proper divisors (115991).

639832681 is a wasteful number, since it uses less digits than its factorization.

639832681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115990.

The product of its digits is 373248, while the sum is 46.

The square root of 639832681 is about 25294.9141330822. The cubic root of 639832681 is about 861.6987699135.

The spelling of 639832681 in words is "six hundred thirty-nine million, eight hundred thirty-two thousand, six hundred eighty-one".