639834731 has 4 divisors (see below), whose sum is σ = 640780512. Its totient is φ = 638888952.

The previous prime is 639834719. The next prime is 639834737. The reversal of 639834731 is 137438936.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 639834731 - 2¹⁸ = 639572587 is a prime.

It is a super-2 number, since 2×639834731² = 818776965987684722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639834737) 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, 471875 + ... + 473228.

It is an arithmetic number, because the mean of its divisors is an integer number (160195128).

Almost surely, 2^639834731 is an apocalyptic number.

639834731 is a deficient number, since it is larger than the sum of its proper divisors (945781).

639834731 is an equidigital number, since it uses as much as digits as its factorization.

639834731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 945780.

The product of its digits is 326592, while the sum is 44.

The square root of 639834731 is about 25294.9546550295. The cubic root of 639834731 is about 861.6996901961.

The spelling of 639834731 in words is "six hundred thirty-nine million, eight hundred thirty-four thousand, seven hundred thirty-one".