644422420 has 96 divisors (see below), whose sum is σ = 1450939392. Its totient is φ = 240000000.

The previous prime is 644422409. The next prime is 644422423. The reversal of 644422420 is 24224446.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644422423) by changing a digit.

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, 2567295 + ... + 2567545.

It is an arithmetic number, because the mean of its divisors is an integer number (15113952).

Almost surely, 2^644422420 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 644422420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (725469696).

644422420 is an abundant number, since it is smaller than the sum of its proper divisors (806516972).

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

644422420 is a wasteful number, since it uses less digits than its factorization.

644422420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433 (or 431 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 28.

The square root of 644422420 is about 25385.4765564880. The cubic root of 644422420 is about 863.7542829066.

Adding to 644422420 its reverse (24224446), we get a palindrome (668646866).

The spelling of 644422420 in words is "six hundred forty-four million, four hundred twenty-two thousand, four hundred twenty".