644070840 has 512 divisors, whose sum is σ = 2553016320. Its totient is φ = 126517248.

The previous prime is 644070829. The next prime is 644070851. The reversal of 644070840 is 48070446.

It is an interprime number because it is at equal distance from previous prime (644070829) and next prime (644070851).

It is a congruent number.

It is an unprimeable number.

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 127 ways as a sum of consecutive naturals, for example, 12152254 + ... + 12152306.

It is an arithmetic number, because the mean of its divisors is an integer number (4986360).

Almost surely, 2^644070840 is an apocalyptic number.

644070840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644070840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1276508160).

644070840 is an abundant number, since it is smaller than the sum of its proper divisors (1908945480).

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

644070840 is a wasteful number, since it uses less digits than its factorization.

644070840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151 (or 147 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 33.

The square root of 644070840 is about 25378.5507860477. The cubic root of 644070840 is about 863.5971737576.

The spelling of 644070840 in words is "six hundred forty-four million, seventy thousand, eight hundred forty".