644340740 has 12 divisors (see below), whose sum is σ = 1353115596. Its totient is φ = 257736288.

The previous prime is 644340737. The next prime is 644340761. The reversal of 644340740 is 47043446.

It can be written as a sum of positive squares in 2 ways, for example, as 392356864 + 251983876 = 19808^2 + 15874^2 .

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 644340697 and 644340706.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16108499 + ... + 16108538.

It is an arithmetic number, because the mean of its divisors is an integer number (112759633).

Almost surely, 2^644340740 is an apocalyptic number.

It is an amenable number.

644340740 is an abundant number, since it is smaller than the sum of its proper divisors (708774856).

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

644340740 is a wasteful number, since it uses less digits than its factorization.

644340740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32217046 (or 32217044 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 32.

The square root of 644340740 is about 25383.8677115998. The cubic root of 644340740 is about 863.7177879882.

The spelling of 644340740 in words is "six hundred forty-four million, three hundred forty thousand, seven hundred forty".