638881992 has 288 divisors, whose sum is σ = 2203437600. Its totient is φ = 172440576.

The previous prime is 638881987. The next prime is 638881993. The reversal of 638881992 is 299188836.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

Its product of digits (1492992) is a multiple of the sum of its prime divisors (384).

It is not an unprimeable number, because it can be changed into a prime (638881993) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1809688 + ... + 1810040.

It is an arithmetic number, because the mean of its divisors is an integer number (7650825).

Almost surely, 2^638881992 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638881992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1101718800).

638881992 is an abundant number, since it is smaller than the sum of its proper divisors (1564555608).

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

638881992 is a wasteful number, since it uses less digits than its factorization.

638881992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 407 (or 384 counting only the distinct ones).

The product of its digits is 1492992, while the sum is 54.

The square root of 638881992 is about 25276.1150495878. The cubic root of 638881992 is about 861.2717761912.

The spelling of 638881992 in words is "six hundred thirty-eight million, eight hundred eighty-one thousand, nine hundred ninety-two".