644440218 has 16 divisors (see below), whose sum is σ = 1316304000. Its totient is φ = 210242816.

The previous prime is 644440217. The next prime is 644440219. The reversal of 644440218 is 812044446.

It is an interprime number because it is at equal distance from previous prime (644440217) and next prime (644440219).

It is not an unprimeable number, because it can be changed into a prime (644440217) 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, 1142343 + ... + 1142906.

It is an arithmetic number, because the mean of its divisors is an integer number (82269000).

Almost surely, 2^644440218 is an apocalyptic number.

644440218 is an abundant number, since it is smaller than the sum of its proper divisors (671863782).

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

644440218 is a wasteful number, since it uses less digits than its factorization.

644440218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2285301.

The product of its (nonzero) digits is 24576, while the sum is 33.

The square root of 644440218 is about 25385.8271088417. The cubic root of 644440218 is about 863.7622347079.

The spelling of 644440218 in words is "six hundred forty-four million, four hundred forty thousand, two hundred eighteen".