639972261 has 24 divisors (see below), whose sum is σ = 958464000. Its totient is φ = 410995872.

The previous prime is 639972241. The next prime is 639972271. The reversal of 639972261 is 162279936.

It is a happy number.

639972261 is a `hidden beast` number, since 639 + 9 + 7 + 2 + 2 + 6 + 1 = 666.

It is not a de Polignac number, because 639972261 - 2⁶ = 639972197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639972241) 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, 122460 + ... + 127578.

It is an arithmetic number, because the mean of its divisors is an integer number (39936000).

Almost surely, 2^639972261 is an apocalyptic number.

It is an amenable number.

639972261 is a deficient number, since it is larger than the sum of its proper divisors (318491739).

639972261 is a wasteful number, since it uses less digits than its factorization.

639972261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5633 (or 5630 counting only the distinct ones).

The product of its digits is 244944, while the sum is 45.

The square root of 639972261 is about 25297.6730352813. The cubic root of 639972261 is about 861.7614254446.

The spelling of 639972261 in words is "six hundred thirty-nine million, nine hundred seventy-two thousand, two hundred sixty-one".