638881380 has 36 divisors (see below), whose sum is σ = 1937940732. Its totient is φ = 170368320.

The previous prime is 638881361. The next prime is 638881409. The reversal of 638881380 is 83188836.

638881380 is a `hidden beast` number, since 638 + 8 + 8 + 1 + 3 + 8 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 443776356 + 195105024 = 21066^2 + 13968^2 .

It is a tau number, because it is divible by the number of its divisors (36).

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 11 ways as a sum of consecutive naturals, for example, 1774491 + ... + 1774850.

It is an arithmetic number, because the mean of its divisors is an integer number (53831687).

Almost surely, 2^638881380 is an apocalyptic number.

638881380 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

638881380 is an abundant number, since it is smaller than the sum of its proper divisors (1299059352).

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

638881380 is a wasteful number, since it uses less digits than its factorization.

638881380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3549356 (or 3549351 counting only the distinct ones).

The product of its (nonzero) digits is 221184, while the sum is 45.

The square root of 638881380 is about 25276.1029432941. The cubic root of 638881380 is about 861.2715011804.

The spelling of 638881380 in words is "six hundred thirty-eight million, eight hundred eighty-one thousand, three hundred eighty".