639811 has 4 divisors (see below), whose sum is σ = 653472. Its totient is φ = 626152.

The previous prime is 639757. The next prime is 639833. The reversal of 639811 is 118936.

It is a happy number.

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 639811 - 2⁹ = 639299 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 639811.

It is not an unprimeable number, because it can be changed into a prime (639851) 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, 6760 + ... + 6853.

It is an arithmetic number, because the mean of its divisors is an integer number (163368).

2⁶³⁹⁸¹¹ is an apocalyptic number.

639811 is a deficient number, since it is larger than the sum of its proper divisors (13661).

639811 is a wasteful number, since it uses less digits than its factorization.

639811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13660.

The product of its digits is 1296, while the sum is 28.

The square root of 639811 is about 799.8818662778. The cubic root of 639811 is about 86.1689036795.

The spelling of 639811 in words is "six hundred thirty-nine thousand, eight hundred eleven".