639919971 has 12 divisors (see below), whose sum is σ = 936991848. Its totient is φ = 420768864.

The previous prime is 639919927. The next prime is 639919997. The reversal of 639919971 is 179919936.

It is not a de Polignac number, because 639919971 - 2⁷ = 639919843 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639919901) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 486345 + ... + 487658.

It is an arithmetic number, because the mean of its divisors is an integer number (78082654).

Almost surely, 2^639919971 is an apocalyptic number.

639919971 is a deficient number, since it is larger than the sum of its proper divisors (297071877).

639919971 is a wasteful number, since it uses less digits than its factorization.

639919971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 974082 (or 974079 counting only the distinct ones).

The product of its digits is 826686, while the sum is 54.

The square root of 639919971 is about 25296.6395199046. The cubic root of 639919971 is about 861.7379542542.

The spelling of 639919971 in words is "six hundred thirty-nine million, nine hundred nineteen thousand, nine hundred seventy-one".