638436 has 24 divisors (see below), whose sum is σ = 1509984. Its totient is φ = 209920.

The previous prime is 638431. The next prime is 638437. The reversal of 638436 is 634836.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 638436.

It is not an unprimeable number, because it can be changed into a prime (638431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 676 + ... + 1316.

It is an arithmetic number, because the mean of its divisors is an integer number (62916).

2⁶³⁸⁴³⁶ is an apocalyptic number.

It is an amenable number.

638436 is an abundant number, since it is smaller than the sum of its proper divisors (871548).

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

638436 is a wasteful number, since it uses less digits than its factorization.

638436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 731 (or 729 counting only the distinct ones).

The product of its digits is 10368, while the sum is 30.

The square root of 638436 is about 799.0219020778. The cubic root of 638436 is about 86.1071316772.

Subtracting from 638436 its reverse (634836), we obtain a square (3600 = 60²).

The spelling of 638436 in words is "six hundred thirty-eight thousand, four hundred thirty-six".