638902840 has 64 divisors (see below), whose sum is σ = 1531172160. Its totient is φ = 239093760.

The previous prime is 638902829. The next prime is 638902841. The reversal of 638902840 is 48209836.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 638902793 and 638902802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638902841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 114925 + ... + 120355.

It is an arithmetic number, because the mean of its divisors is an integer number (23924565).

Almost surely, 2^638902840 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 638902840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (765586080).

638902840 is an abundant number, since it is smaller than the sum of its proper divisors (892269320).

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

638902840 is a wasteful number, since it uses less digits than its factorization.

638902840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5632 (or 5628 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 40.

The square root of 638902840 is about 25276.5274513727. The cubic root of 638902840 is about 861.2811444308.

The spelling of 638902840 in words is "six hundred thirty-eight million, nine hundred two thousand, eight hundred forty".