639744381 has 12 divisors (see below), whose sum is σ = 927912700. Its totient is φ = 424725120.

The previous prime is 639744337. The next prime is 639744431. The reversal of 639744381 is 183447936.

639744381 is a `hidden beast` number, since 639 + 7 + 4 + 4 + 3 + 8 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 591219225 + 48525156 = 24315^2 + 6966^2 .

It is not a de Polignac number, because 639744381 - 2⁷ = 639744253 is a prime.

It is a super-2 number, since 2×639744381² = 818545746042146322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639744311) 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, 145306 + ... + 149643.

Almost surely, 2^639744381 is an apocalyptic number.

It is an amenable number.

639744381 is a deficient number, since it is larger than the sum of its proper divisors (288168319).

639744381 is a wasteful number, since it uses less digits than its factorization.

639744381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 295196 (or 295193 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The square root of 639744381 is about 25293.1686627042. The cubic root of 639744381 is about 861.6591285593.

The spelling of 639744381 in words is "six hundred thirty-nine million, seven hundred forty-four thousand, three hundred eighty-one".