638709720 has 128 divisors (see below), whose sum is σ = 2213360640. Its totient is φ = 145725440.

The previous prime is 638709691. The next prime is 638709739. The reversal of 638709720 is 27907836.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8209 + ... + 36671.

It is an arithmetic number, because the mean of its divisors is an integer number (17291880).

Almost surely, 2^638709720 is an apocalyptic number.

638709720 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 638709720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1106680320).

638709720 is an abundant number, since it is smaller than the sum of its proper divisors (1574650920).

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

638709720 is a wasteful number, since it uses less digits than its factorization.

638709720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28505 (or 28501 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 42.

The square root of 638709720 is about 25272.7070176505. The cubic root of 638709720 is about 861.1943563905.

The spelling of 638709720 in words is "six hundred thirty-eight million, seven hundred nine thousand, seven hundred twenty".