639809279 has 4 divisors (see below), whose sum is σ = 660448320. Its totient is φ = 619170240.

The previous prime is 639809273. The next prime is 639809293. The reversal of 639809279 is 972908936.

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 639809279 - 2²⁴ = 623032063 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639809279.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639809273) 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, 10319474 + ... + 10319535.

It is an arithmetic number, because the mean of its divisors is an integer number (165112080).

Almost surely, 2^639809279 is an apocalyptic number.

639809279 is a deficient number, since it is larger than the sum of its proper divisors (20639041).

639809279 is a wasteful number, since it uses less digits than its factorization.

639809279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20639040.

The product of its (nonzero) digits is 1469664, while the sum is 53.

The square root of 639809279 is about 25294.4515457442. The cubic root of 639809279 is about 861.6882641875.

The spelling of 639809279 in words is "six hundred thirty-nine million, eight hundred nine thousand, two hundred seventy-nine".