638791 has 4 divisors (see below), whose sum is σ = 640584. Its totient is φ = 637000.

The previous prime is 638767. The next prime is 638801. The reversal of 638791 is 197836.

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

It is a cyclic number.

It is not a de Polignac number, because 638791 - 2⁷ = 638663 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (633791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 160 + ... + 1141.

It is an arithmetic number, because the mean of its divisors is an integer number (160146).

2⁶³⁸⁷⁹¹ is an apocalyptic number.

638791 is a deficient number, since it is larger than the sum of its proper divisors (1793).

638791 is a wasteful number, since it uses less digits than its factorization.

638791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1792.

The product of its digits is 9072, while the sum is 34.

The square root of 638791 is about 799.2440178068. The cubic root of 638791 is about 86.1230885717.

The spelling of 638791 in words is "six hundred thirty-eight thousand, seven hundred ninety-one".