645389640 has 128 divisors (see below), whose sum is σ = 2458656000. Its totient is φ = 147515904.

The previous prime is 645389629. The next prime is 645389659. The reversal of 645389640 is 46983546.

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, 35125 + ... + 50244.

It is an arithmetic number, because the mean of its divisors is an integer number (19208250).

Almost surely, 2^645389640 is an apocalyptic number.

645389640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645389640 is an abundant number, since it is smaller than the sum of its proper divisors (1813266360).

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

645389640 is a wasteful number, since it uses less digits than its factorization.

645389640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85396 (or 85386 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 45.

The square root of 645389640 is about 25404.5200702552. The cubic root of 645389640 is about 864.1862060087.

The spelling of 645389640 in words is "six hundred forty-five million, three hundred eighty-nine thousand, six hundred forty".