639723 has 16 divisors (see below), whose sum is σ = 999936. Its totient is φ = 356160.

The previous prime is 639719. The next prime is 639731. The reversal of 639723 is 327936.

It is a happy number.

It is not a de Polignac number, because 639723 - 2² = 639719 is a prime.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (639703) 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 15 ways as a sum of consecutive naturals, for example, 490 + ... + 1232.

It is an arithmetic number, because the mean of its divisors is an integer number (62496).

2⁶³⁹⁷²³ is an apocalyptic number.

639723 is a deficient number, since it is larger than the sum of its proper divisors (360213).

639723 is a wasteful number, since it uses less digits than its factorization.

639723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 794.

The product of its digits is 6804, while the sum is 30.

The square root of 639723 is about 799.8268562633. The cubic root of 639723 is about 86.1649529236.

The spelling of 639723 in words is "six hundred thirty-nine thousand, seven hundred twenty-three".