638405 has 4 divisors (see below), whose sum is σ = 766092. Its totient is φ = 510720.

The previous prime is 638371. The next prime is 638423. The reversal of 638405 is 504836.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 231361 + 407044 = 481^2 + 638^2 .

It is a de Polignac number, because none of the positive numbers 2^k-638405 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63836 + ... + 63845.

It is an arithmetic number, because the mean of its divisors is an integer number (191523).

2⁶³⁸⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

638405 is a deficient number, since it is larger than the sum of its proper divisors (127687).

638405 is a wasteful number, since it uses less digits than its factorization.

638405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127686.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 638405 is about 799.0025031250. The cubic root of 638405 is about 86.1057379775.

The spelling of 638405 in words is "six hundred thirty-eight thousand, four hundred five".