638873640 has 48 divisors (see below), whose sum is σ = 2076340500. Its totient is φ = 170366208.

The previous prime is 638873621. The next prime is 638873647. The reversal of 638873640 is 46378836.

638873640 is a `hidden beast` number, since 638 + 8 + 7 + 3 + 6 + 4 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 629909604 + 8964036 = 25098^2 + 2994^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (638873647) 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, 886965 + ... + 887684.

Almost surely, 2^638873640 is an apocalyptic number.

638873640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

638873640 is an abundant number, since it is smaller than the sum of its proper divisors (1437466860).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

638873640 is a wasteful number, since it uses less digits than its factorization.

638873640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1774666 (or 1774659 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 45.

The square root of 638873640 is about 25275.9498337847. The cubic root of 638873640 is about 861.2680230864.

The spelling of 638873640 in words is "six hundred thirty-eight million, eight hundred seventy-three thousand, six hundred forty".