644202444420 has 36 divisors (see below), whose sum is σ = 1954080748620. Its totient is φ = 171787318464.

The previous prime is 644202444401. The next prime is 644202444469. The reversal of 644202444420 is 24444202446.

644202444420 is a `hidden beast` number, since 6 + 4 + 4 + 202 + 4 + 4 + 442 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 342056540736 + 302145903684 = 584856^2 + 549678^2 .

It is a tau number, because it is divible by the number of its divisors (36).

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 11 ways as a sum of consecutive naturals, for example, 1789451055 + ... + 1789451414.

It is an arithmetic number, because the mean of its divisors is an integer number (54280020795).

Almost surely, 2^644202444420 is an apocalyptic number.

644202444420 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644202444420 is an abundant number, since it is smaller than the sum of its proper divisors (1309878304200).

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

644202444420 is a wasteful number, since it uses less digits than its factorization.

644202444420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3578902484 (or 3578902479 counting only the distinct ones).

The product of its (nonzero) digits is 196608, while the sum is 36.

Adding to 644202444420 its reverse (24444202446), we get a palindrome (668646646866).

The spelling of 644202444420 in words is "six hundred forty-four billion, two hundred two million, four hundred forty-four thousand, four hundred twenty".