644340018 has 32 divisors (see below), whose sum is σ = 1559412864. Its totient is φ = 173267712.

The previous prime is 644340017. The next prime is 644340019. The reversal of 644340018 is 810043446.

It is an interprime number because it is at equal distance from previous prime (644340017) and next prime (644340019).

It is not an unprimeable number, because it can be changed into a prime (644340013) 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, 450505 + ... + 451932.

It is an arithmetic number, because the mean of its divisors is an integer number (48731652).

Almost surely, 2^644340018 is an apocalyptic number.

644340018 is an abundant number, since it is smaller than the sum of its proper divisors (915072846).

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

644340018 is a wasteful number, since it uses less digits than its factorization.

644340018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 902466.

The product of its (nonzero) digits is 9216, while the sum is 30.

The square root of 644340018 is about 25383.8534899648. The cubic root of 644340018 is about 863.7174653823.

The spelling of 644340018 in words is "six hundred forty-four million, three hundred forty thousand, eighteen".