639291 has 4 divisors (see below), whose sum is σ = 852392. Its totient is φ = 426192.

The previous prime is 639269. The next prime is 639299. The reversal of 639291 is 192936.

639291 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 639291 - 2⁵ = 639259 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639299) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106546 + ... + 106551.

It is an arithmetic number, because the mean of its divisors is an integer number (213098).

2⁶³⁹²⁹¹ is an apocalyptic number.

639291 is a deficient number, since it is larger than the sum of its proper divisors (213101).

639291 is a wasteful number, since it uses less digits than its factorization.

639291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213100.

The product of its digits is 2916, while the sum is 30.

The square root of 639291 is about 799.5567522071. The cubic root of 639291 is about 86.1455530471.

The spelling of 639291 in words is "six hundred thirty-nine thousand, two hundred ninety-one".