644342140 has 24 divisors (see below), whose sum is σ = 1457205120. Its totient is φ = 237910848.

The previous prime is 644342137. The next prime is 644342141. The reversal of 644342140 is 41243446.

It is a junction number, because it is equal to n+sod(n) for n = 644342099 and 644342108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644342141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1238860 + ... + 1239379.

It is an arithmetic number, because the mean of its divisors is an integer number (60716880).

Almost surely, 2^644342140 is an apocalyptic number.

It is an amenable number.

644342140 is an abundant number, since it is smaller than the sum of its proper divisors (812862980).

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

644342140 is a wasteful number, since it uses less digits than its factorization.

644342140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2478261 (or 2478259 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 28.

The square root of 644342140 is about 25383.8952881547. The cubic root of 644342140 is about 863.7184135393.

Adding to 644342140 its reverse (41243446), we get a palindrome (685585586).

The spelling of 644342140 in words is "six hundred forty-four million, three hundred forty-two thousand, one hundred forty".