638743440 has 160 divisors (see below), whose sum is σ = 2042726400. Its totient is φ = 165035520.

The previous prime is 638743429. The next prime is 638743447. The reversal of 638743440 is 44347836.

It is not an unprimeable number, because it can be changed into a prime (638743447) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1118355 + ... + 1118925.

It is an arithmetic number, because the mean of its divisors is an integer number (12767040).

Almost surely, 2^638743440 is an apocalyptic number.

638743440 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 638743440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1021363200).

638743440 is an abundant number, since it is smaller than the sum of its proper divisors (1403982960).

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

638743440 is a wasteful number, since it uses less digits than its factorization.

638743440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 725 (or 719 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 39.

The square root of 638743440 is about 25273.3741316825. The cubic root of 638743440 is about 861.2095114037.

The spelling of 638743440 in words is "six hundred thirty-eight million, seven hundred forty-three thousand, four hundred forty".