645998444 has 72 divisors (see below), whose sum is σ = 1407829248. Its totient is φ = 253955520.

The previous prime is 645998413. The next prime is 645998459. The reversal of 645998444 is 444899546.

It is a super-2 number, since 2×645998444² = 834627979300842272, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 998129 + ... + 998775.

It is an arithmetic number, because the mean of its divisors is an integer number (19553184).

Almost surely, 2^645998444 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 645998444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (703914624).

645998444 is an abundant number, since it is smaller than the sum of its proper divisors (761830804).

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

645998444 is a wasteful number, since it uses less digits than its factorization.

645998444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 895 (or 880 counting only the distinct ones).

The product of its digits is 4976640, while the sum is 53.

The square root of 645998444 is about 25416.4994442586. The cubic root of 645998444 is about 864.4578531095.

The spelling of 645998444 in words is "six hundred forty-five million, nine hundred ninety-eight thousand, four hundred forty-four".