639648 has 36 divisors (see below), whose sum is σ = 1819818. Its totient is φ = 213120.

The previous prime is 639647. The next prime is 639671. The reversal of 639648 is 846936.

639648 is a `hidden beast` number, since 6 + 3 + 9 + 648 = 666.

It can be written as a sum of positive squares in only one way, i.e., 501264 + 138384 = 708^2 + 372^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is an Ulam number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639648.

It is not an unprimeable number, because it can be changed into a prime (639647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 823 + ... + 1398.

2⁶³⁹⁶⁴⁸ is an apocalyptic number.

It is an amenable number.

639648 is an abundant number, since it is smaller than the sum of its proper divisors (1180170).

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

639648 is a wasteful number, since it uses less digits than its factorization.

639648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2237 (or 2226 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 639648 is about 799.7799697417. The cubic root of 639648 is about 86.1615855161.

The spelling of 639648 in words is "six hundred thirty-nine thousand, six hundred forty-eight".