639951941 has 4 divisors (see below), whose sum is σ = 660595584. Its totient is φ = 619308300.

The previous prime is 639951887. The next prime is 639951943. The reversal of 639951941 is 149159936.

It is a happy number.

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 639951941 - 2¹⁸ = 639689797 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 (639951943) 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, 10321775 + ... + 10321836.

It is an arithmetic number, because the mean of its divisors is an integer number (165148896).

Almost surely, 2^639951941 is an apocalyptic number.

It is an amenable number.

639951941 is a deficient number, since it is larger than the sum of its proper divisors (20643643).

639951941 is a wasteful number, since it uses less digits than its factorization.

639951941 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20643642.

The product of its digits is 262440, while the sum is 47.

The square root of 639951941 is about 25297.2714141269. The cubic root of 639951941 is about 861.7523046443.

The spelling of 639951941 in words is "six hundred thirty-nine million, nine hundred fifty-one thousand, nine hundred forty-one".