639992 has 8 divisors (see below), whose sum is σ = 1200000. Its totient is φ = 319992.

The previous prime is 639983. The next prime is 639997. The reversal of 639992 is 299936.

It is a tau number, because it is divible by the number of its divisors (8).

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 (639997) by changing a digit.

639992 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 as a sum of consecutive naturals, namely, 39992 + ... + 40007.

It is an arithmetic number, because the mean of its divisors is an integer number (150000).

2⁶³⁹⁹⁹² is an apocalyptic number.

It is an amenable number.

639992 is a deficient number, since it is larger than the sum of its proper divisors (560008).

639992 is a wasteful number, since it uses less digits than its factorization.

639992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80005 (or 80001 counting only the distinct ones).

The product of its digits is 26244, while the sum is 38.

The square root of 639992 is about 799.9949999844. The cubic root of 639992 is about 86.1770285273.

The spelling of 639992 in words is "six hundred thirty-nine thousand, nine hundred ninety-two".