639973971 has 24 divisors (see below), whose sum is σ = 1137732960. Its totient is φ = 337568256.

The previous prime is 639973969. The next prime is 639973981. The reversal of 639973971 is 179379936.

It is not a de Polignac number, because 639973971 - 2¹ = 639973969 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639973921) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 389886 + ... + 391523.

It is an arithmetic number, because the mean of its divisors is an integer number (47405540).

Almost surely, 2^639973971 is an apocalyptic number.

639973971 is a deficient number, since it is larger than the sum of its proper divisors (497758989).

639973971 is a wasteful number, since it uses less digits than its factorization.

639973971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 781435 (or 781432 counting only the distinct ones).

The product of its digits is 1928934, while the sum is 54.

The square root of 639973971 is about 25297.7068328337. The cubic root of 639973971 is about 861.7621929834.

The spelling of 639973971 in words is "six hundred thirty-nine million, nine hundred seventy-three thousand, nine hundred seventy-one".