645578640 has 160 divisors (see below), whose sum is σ = 2541384960. Its totient is φ = 147557376.

The previous prime is 645578629. The next prime is 645578671. The reversal of 645578640 is 46875546.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 6229 + ... + 36468.

It is an arithmetic number, because the mean of its divisors is an integer number (15883656).

Almost surely, 2^645578640 is an apocalyptic number.

645578640 is a gapful number since it is divisible by the number (60) 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 645578640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1270692480).

645578640 is an abundant number, since it is smaller than the sum of its proper divisors (1895806320).

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

645578640 is a wasteful number, since it uses less digits than its factorization.

645578640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42726 (or 42714 counting only the distinct ones).

The product of its (nonzero) digits is 806400, while the sum is 45.

The square root of 645578640 is about 25408.2396084420. The cubic root of 645578640 is about 864.2705557006.

The spelling of 645578640 in words is "six hundred forty-five million, five hundred seventy-eight thousand, six hundred forty".