644420428 has 24 divisors (see below), whose sum is σ = 1216609632. Its totient is φ = 297533184.

The previous prime is 644420423. The next prime is 644420443. The reversal of 644420428 is 824024446.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a junction number, because it is equal to n+sod(n) for n = 644420393 and 644420402.

It is not an unprimeable number, because it can be changed into a prime (644420423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 85800 + ... + 93007.

It is an arithmetic number, because the mean of its divisors is an integer number (50692068).

Almost surely, 2^644420428 is an apocalyptic number.

644420428 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

644420428 is a deficient number, since it is larger than the sum of its proper divisors (572189204).

644420428 is a wasteful number, since it uses less digits than its factorization.

644420428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178881 (or 178879 counting only the distinct ones).

The product of its (nonzero) digits is 49152, while the sum is 34.

The square root of 644420428 is about 25385.4373214251. The cubic root of 644420428 is about 863.7533929105.

The spelling of 644420428 in words is "six hundred forty-four million, four hundred twenty thousand, four hundred twenty-eight".