639996 has 48 divisors (see below), whose sum is σ = 1800960. Its totient is φ = 172800.

The previous prime is 639983. The next prime is 639997. The reversal of 639996 is 699936.

639996 = T₃₁ + T₃₂ + ... + T₁₅₆.

It is a Harshad number since it is a multiple of its sum of digits (42).

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.

639996 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1396 + ... + 1796.

It is an arithmetic number, because the mean of its divisors is an integer number (37520).

2⁶³⁹⁹⁹⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639996, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (900480).

639996 is an abundant number, since it is smaller than the sum of its proper divisors (1160964).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639996 is a wasteful number, since it uses less digits than its factorization.

639996 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 434 (or 432 counting only the distinct ones).

The product of its digits is 78732, while the sum is 42.

The square root of 639996 is about 799.9974999961. The cubic root of 639996 is about 86.1772080647.

The spelling of 639996 in words is "six hundred thirty-nine thousand, nine hundred ninety-six".