638391 has 8 divisors (see below), whose sum is σ = 916720. Its totient is φ = 392832.

The previous prime is 638371. The next prime is 638423. The reversal of 638391 is 193836.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 638391 - 2⁵ = 638359 is a prime.

It is a Duffinian number.

638391 is a lucky number.

It is a plaindrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638371) 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, 8146 + ... + 8223.

It is an arithmetic number, because the mean of its divisors is an integer number (114590).

2⁶³⁸³⁹¹ is an apocalyptic number.

638391 is a deficient number, since it is larger than the sum of its proper divisors (278329).

638391 is a wasteful number, since it uses less digits than its factorization.

638391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16385.

The product of its digits is 3888, while the sum is 30.

The square root of 638391 is about 798.9937421532. The cubic root of 638391 is about 86.1051085499.

The spelling of 638391 in words is "six hundred thirty-eight thousand, three hundred ninety-one".