645997840 has 40 divisors (see below), whose sum is σ = 1550400768. Its totient is φ = 250062720.

The previous prime is 645997829. The next prime is 645997861. The reversal of 645997840 is 48799546.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 127762 + ... + 132721.

Almost surely, 2^645997840 is an apocalyptic number.

It is an amenable number.

645997840 is an abundant number, since it is smaller than the sum of its proper divisors (904402928).

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

645997840 is a wasteful number, since it uses less digits than its factorization.

645997840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 260527 (or 260521 counting only the distinct ones).

The product of its (nonzero) digits is 2177280, while the sum is 52.

The square root of 645997840 is about 25416.4875622105. The cubic root of 645997840 is about 864.4575836905.

The spelling of 645997840 in words is "six hundred forty-five million, nine hundred ninety-seven thousand, eight hundred forty".