638491 has 8 divisors (see below), whose sum is σ = 743904. Its totient is φ = 536640.

The previous prime is 638489. The next prime is 638501. The reversal of 638491 is 194836.

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

It is a cyclic number.

It is not a de Polignac number, because 638491 - 2¹ = 638489 is a prime.

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, 490 + ... + 1231.

It is an arithmetic number, because the mean of its divisors is an integer number (92988).

2⁶³⁸⁴⁹¹ is an apocalyptic number.

638491 is a deficient number, since it is larger than the sum of its proper divisors (105413).

638491 is a wasteful number, since it uses less digits than its factorization.

638491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1781.

The product of its digits is 5184, while the sum is 31.

The square root of 638491 is about 799.0563184157. The cubic root of 638491 is about 86.1096042593.

The spelling of 638491 in words is "six hundred thirty-eight thousand, four hundred ninety-one".