638690400 has 144 divisors (see below), whose sum is σ = 2310008400. Its totient is φ = 170311680.

The previous prime is 638690387. The next prime is 638690401. The reversal of 638690400 is 4096836.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638690401) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6816 + ... + 36384.

It is an arithmetic number, because the mean of its divisors is an integer number (16041725).

Almost surely, 2^638690400 is an apocalyptic number.

638690400 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 638690400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1155004200).

638690400 is an abundant number, since it is smaller than the sum of its proper divisors (1671318000).

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

638690400 is a wasteful number, since it uses less digits than its factorization.

638690400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29598 (or 29579 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 638690400 is about 25272.3247842378. The cubic root of 638690400 is about 861.1856730287.

The spelling of 638690400 in words is "six hundred thirty-eight million, six hundred ninety thousand, four hundred".