638673840 has 360 divisors, whose sum is σ = 2559153168. Its totient is φ = 142248960.

The previous prime is 638673823. The next prime is 638673857. The reversal of 638673840 is 48376836.

638673840 is a `hidden beast` number, since 638 + 6 + 7 + 3 + 8 + 4 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (638673823) and next prime (638673857).

It is a tau number, because it is divible by the number of its divisors (360).

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

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1516830 + ... + 1517250.

Almost surely, 2^638673840 is an apocalyptic number.

638673840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638673840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1279576584).

638673840 is an abundant number, since it is smaller than the sum of its proper divisors (1920479328).

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

638673840 is a wasteful number, since it uses less digits than its factorization.

638673840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 497 (or 481 counting only the distinct ones).

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

The square root of 638673840 is about 25271.9971509970. The cubic root of 638673840 is about 861.1782300078.

The spelling of 638673840 in words is "six hundred thirty-eight million, six hundred seventy-three thousand, eight hundred forty".