639964943 has 4 divisors (see below), whose sum is σ = 647675448. Its totient is φ = 632254440.

The previous prime is 639964937. The next prime is 639964951. The reversal of 639964943 is 349469936.

It is a happy number.

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 639964943 - 2⁶ = 639964879 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639964933) 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, 3855128 + ... + 3855293.

It is an arithmetic number, because the mean of its divisors is an integer number (161918862).

Almost surely, 2^639964943 is an apocalyptic number.

639964943 is a deficient number, since it is larger than the sum of its proper divisors (7710505).

639964943 is an equidigital number, since it uses as much as digits as its factorization.

639964943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7710504.

The product of its digits is 3779136, while the sum is 53.

The square root of 639964943 is about 25297.5283970589. The cubic root of 639964943 is about 861.7581407219.

The spelling of 639964943 in words is "six hundred thirty-nine million, nine hundred sixty-four thousand, nine hundred forty-three".