644042420 has 48 divisors (see below), whose sum is σ = 1567496448. Its totient is φ = 217701120.

The previous prime is 644042419. The next prime is 644042423. The reversal of 644042420 is 24240446.

644042420 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 644042420.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644042423) 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, 22457 + ... + 42336.

It is an arithmetic number, because the mean of its divisors is an integer number (32656176).

Almost surely, 2^644042420 is an apocalyptic number.

It is an amenable number.

644042420 is an abundant number, since it is smaller than the sum of its proper divisors (923454028).

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

644042420 is a wasteful number, since it uses less digits than its factorization.

644042420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64880 (or 64878 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 26.

The square root of 644042420 is about 25377.9908582220. The cubic root of 644042420 is about 863.5844713285.

Adding to 644042420 its reverse (24240446), we get a palindrome (668282866).

The spelling of 644042420 in words is "six hundred forty-four million, forty-two thousand, four hundred twenty".