638406 has 24 divisors (see below), whose sum is σ = 1432080. Its totient is φ = 205296.

The previous prime is 638371. The next prime is 638423. The reversal of 638406 is 604836.

638406 = 398² + 399² + ... + 401².

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 638406.

It is a congruent number.

It is an unprimeable number.

638406 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 90 + ... + 1133.

It is an arithmetic number, because the mean of its divisors is an integer number (59670).

2⁶³⁸⁴⁰⁶ is an apocalyptic number.

638406 is an abundant number, since it is smaller than the sum of its proper divisors (793674).

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

638406 is a wasteful number, since it uses less digits than its factorization.

638406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1260 (or 1257 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 638406 is about 799.0031289050. The cubic root of 638406 is about 86.1057829362.

The spelling of 638406 in words is "six hundred thirty-eight thousand, four hundred six".