644655270 has 144 divisors (see below), whose sum is σ = 1883694960. Its totient is φ = 140773248.

The previous prime is 644655241. The next prime is 644655289. The reversal of 644655270 is 72556446.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 777216 + ... + 778044.

It is an arithmetic number, because the mean of its divisors is an integer number (13081215).

Almost surely, 2^644655270 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644655270, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (941847480).

644655270 is an abundant number, since it is smaller than the sum of its proper divisors (1239039690).

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

644655270 is a wasteful number, since it uses less digits than its factorization.

644655270 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 899 (or 869 counting only the distinct ones).

The product of its (nonzero) digits is 201600, while the sum is 39.

The square root of 644655270 is about 25390.0624260753. The cubic root of 644655270 is about 863.8583042023.

It can be divided in two parts, 6446 and 55270, that added together give a palindrome (61716).

The spelling of 644655270 in words is "six hundred forty-four million, six hundred fifty-five thousand, two hundred seventy".