644248620 has 96 divisors (see below), whose sum is σ = 2009918400. Its totient is φ = 171320832.

The previous prime is 644248589. The next prime is 644248667. The reversal of 644248620 is 26842446.

It is a happy number.

644248620 is a `hidden beast` number, since 6 + 4 + 4 + 24 + 8 + 620 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 219402 + ... + 222318.

It is an arithmetic number, because the mean of its divisors is an integer number (20936650).

Almost surely, 2^644248620 is an apocalyptic number.

644248620 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 644248620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1004959200).

644248620 is an abundant number, since it is smaller than the sum of its proper divisors (1365669780).

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

644248620 is a wasteful number, since it uses less digits than its factorization.

644248620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3344 (or 3336 counting only the distinct ones).

The product of its (nonzero) digits is 73728, while the sum is 36.

The square root of 644248620 is about 25382.0531084465. The cubic root of 644248620 is about 863.6766247394.

The spelling of 644248620 in words is "six hundred forty-four million, two hundred forty-eight thousand, six hundred twenty".