638557380 has 144 divisors (see below), whose sum is σ = 2019654000. Its totient is φ = 163107840.

The previous prime is 638557379. The next prime is 638557393. The reversal of 638557380 is 83755836.

638557380 is a `hidden beast` number, since 63 + 8 + 557 + 38 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 94361796 + 544195584 = 9714^2 + 23328^2 .

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 47 ways as a sum of consecutive naturals, for example, 777370 + ... + 778190.

It is an arithmetic number, because the mean of its divisors is an integer number (14025375).

Almost surely, 2^638557380 is an apocalyptic number.

638557380 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 638557380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1009827000).

638557380 is an abundant number, since it is smaller than the sum of its proper divisors (1381096620).

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

638557380 is a wasteful number, since it uses less digits than its factorization.

638557380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1014 (or 1009 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 45.

The square root of 638557380 is about 25269.6929146359. The cubic root of 638557380 is about 861.1258825200.

The spelling of 638557380 in words is "six hundred thirty-eight million, five hundred fifty-seven thousand, three hundred eighty".