645188544 has 448 divisors, whose sum is σ = 2553492480. Its totient is φ = 154275840.

The previous prime is 645188519. The next prime is 645188561. The reversal of 645188544 is 445881546.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (448).

It is a self number, because there is not a number n which added to its sum of digits gives 645188544.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1729542 + ... + 1729914.

It is an arithmetic number, because the mean of its divisors is an integer number (5699760).

Almost surely, 2^645188544 is an apocalyptic number.

645188544 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645188544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1276746240).

645188544 is an abundant number, since it is smaller than the sum of its proper divisors (1908303936).

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

645188544 is a wasteful number, since it uses less digits than its factorization.

645188544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 425 (or 409 counting only the distinct ones).

The product of its digits is 614400, while the sum is 45.

The square root of 645188544 is about 25400.5618835490. The cubic root of 645188544 is about 864.0964398522.

The spelling of 645188544 in words is "six hundred forty-five million, one hundred eighty-eight thousand, five hundred forty-four".