639917 has 4 divisors (see below), whose sum is σ = 649536. Its totient is φ = 630300.

The previous prime is 639911. The next prime is 639937. The reversal of 639917 is 719936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 639917 - 2⁶ = 639853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639911) 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, 4709 + ... + 4842.

It is an arithmetic number, because the mean of its divisors is an integer number (162384).

2⁶³⁹⁹¹⁷ is an apocalyptic number.

639917 is a gapful number since it is divisible by the number (67) formed by its first and last digit.

It is an amenable number.

639917 is a deficient number, since it is larger than the sum of its proper divisors (9619).

639917 is an equidigital number, since it uses as much as digits as its factorization.

639917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9618.

The product of its digits is 10206, while the sum is 35.

The square root of 639917 is about 799.9481233180. The cubic root of 639917 is about 86.1736620636.

The spelling of 639917 in words is "six hundred thirty-nine thousand, nine hundred seventeen".