638509891320 has 768 divisors, whose sum is σ = 2508066063360. Its totient is φ = 137854918656.

The previous prime is 638509891309. The next prime is 638509891337. The reversal of 638509891320 is 23198905836.

638509891320 is a `hidden beast` number, since 6 + 38 + 509 + 89 + 1 + 3 + 20 = 666.

It is a super-2 number, since 2×638509891320² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 419244079 + ... + 419245601.

It is an arithmetic number, because the mean of its divisors is an integer number (3265711020).

Almost surely, 2^638509891320 is an apocalyptic number.

638509891320 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 638509891320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1254033031680).

638509891320 is an abundant number, since it is smaller than the sum of its proper divisors (1869556172040).

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

638509891320 is a wasteful number, since it uses less digits than its factorization.

638509891320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1716 (or 1709 counting only the distinct ones).

The product of its (nonzero) digits is 2799360, while the sum is 54.

The spelling of 638509891320 in words is "six hundred thirty-eight billion, five hundred nine million, eight hundred ninety-one thousand, three hundred twenty".