644805402 has 8 divisors (see below), whose sum is σ = 1289610816. Its totient is φ = 214935132.

The previous prime is 644805389. The next prime is 644805407. The reversal of 644805402 is 204508446.

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

644805402 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (644805407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53733778 + ... + 53733789.

It is an arithmetic number, because the mean of its divisors is an integer number (161201352).

Almost surely, 2^644805402 is an apocalyptic number.

644805402 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

644805402 is a wasteful number, since it uses less digits than its factorization.

644805402 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107467572.

The product of its (nonzero) digits is 30720, while the sum is 33.

The square root of 644805402 is about 25393.0187650070. The cubic root of 644805402 is about 863.9253595285.

The spelling of 644805402 in words is "six hundred forty-four million, eight hundred five thousand, four hundred two".