639974 has 8 divisors (see below), whose sum is σ = 963480. Its totient is φ = 318816.

The previous prime is 639959. The next prime is 639983. The reversal of 639974 is 479936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

639974 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 497 + ... + 1235.

It is an arithmetic number, because the mean of its divisors is an integer number (120435).

2⁶³⁹⁹⁷⁴ is an apocalyptic number.

639974 is a deficient number, since it is larger than the sum of its proper divisors (323506).

639974 is a wasteful number, since it uses less digits than its factorization.

639974 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1174.

The product of its digits is 40824, while the sum is 38.

The square root of 639974 is about 799.9837498350. The cubic root of 639974 is about 86.1762206000.

Subtracting from 639974 its sum of digits (38), we obtain a palindrome (639936).

The spelling of 639974 in words is "six hundred thirty-nine thousand, nine hundred seventy-four".