639799 has 4 divisors (see below), whose sum is σ = 642600. Its totient is φ = 637000.

The previous prime is 639757. The next prime is 639833. The reversal of 639799 is 997936.

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 639799 - 2⁷ = 639671 is a prime.

It is a d-powerful number, because it can be written as 6⁶ + 3⁵ + 7⁴ + 9 + 9⁵ + 9⁶ .

It is a Duffinian number.

639799 is a lucky 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 (639719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1024 + ... + 1525.

It is an arithmetic number, because the mean of its divisors is an integer number (160650).

2⁶³⁹⁷⁹⁹ is an apocalyptic number.

639799 is a deficient number, since it is larger than the sum of its proper divisors (2801).

639799 is a wasteful number, since it uses less digits than its factorization.

639799 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2800.

The product of its digits is 91854, while the sum is 43.

The square root of 639799 is about 799.8743651349. The cubic root of 639799 is about 86.1683649614.

The spelling of 639799 in words is "six hundred thirty-nine thousand, seven hundred ninety-nine".