645927840 has 72 divisors (see below), whose sum is σ = 2204233668. Its totient is φ = 172247040.

The previous prime is 645927839. The next prime is 645927881. The reversal of 645927840 is 48729546.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 636855696 + 9072144 = 25236^2 + 3012^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 222841 + ... + 225720.

Almost surely, 2^645927840 is an apocalyptic number.

645927840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645927840 is an abundant number, since it is smaller than the sum of its proper divisors (1558305828).

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

645927840 is a wasteful number, since it uses less digits than its factorization.

645927840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448582 (or 448571 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The square root of 645927840 is about 25415.1104660200. The cubic root of 645927840 is about 864.4263585001.

The spelling of 645927840 in words is "six hundred forty-five million, nine hundred twenty-seven thousand, eight hundred forty".