644357420 has 96 divisors (see below), whose sum is σ = 1631121408. Its totient is φ = 209037312.

The previous prime is 644357407. The next prime is 644357437. The reversal of 644357420 is 24753446.

It is a Harshad number since it is a multiple of its sum of digits (35).

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 31 ways as a sum of consecutive naturals, for example, 311309 + ... + 313371.

It is an arithmetic number, because the mean of its divisors is an integer number (16990848).

Almost surely, 2^644357420 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 644357420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (815560704).

644357420 is an abundant number, since it is smaller than the sum of its proper divisors (986763988).

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

644357420 is a wasteful number, since it uses less digits than its factorization.

644357420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2199 (or 2197 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 35.

The square root of 644357420 is about 25384.1962646053. The cubic root of 644357420 is about 863.7252409229.

The spelling of 644357420 in words is "six hundred forty-four million, three hundred fifty-seven thousand, four hundred twenty".