644406448 has 80 divisors (see below), whose sum is σ = 1506600000. Its totient is φ = 266585088.

The previous prime is 644406443. The next prime is 644406457. The reversal of 644406448 is 844604446.

It is a self number, because there is not a number n which added to its sum of digits gives 644406448.

It is not an unprimeable number, because it can be changed into a prime (644406443) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 157128 + ... + 161176.

It is an arithmetic number, because the mean of its divisors is an integer number (18832500).

Almost surely, 2^644406448 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 644406448, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (753300000).

644406448 is an abundant number, since it is smaller than the sum of its proper divisors (862193552).

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

644406448 is a wasteful number, since it uses less digits than its factorization.

644406448 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4107 (or 4087 counting only the distinct ones).

The product of its (nonzero) digits is 294912, while the sum is 40.

The square root of 644406448 is about 25385.1619652111. The cubic root of 644406448 is about 863.7471468020.

The spelling of 644406448 in words is "six hundred forty-four million, four hundred six thousand, four hundred forty-eight".