645443640 has 80 divisors (see below), whose sum is σ = 2169418680. Its totient is φ = 172117440.

The previous prime is 645443627. The next prime is 645443671. The reversal of 645443640 is 46344546.

645443640 is a `hidden beast` number, since 6 + 4 + 5 + 4 + 4 + 3 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 645443595 and 645443604.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 96366 + ... + 102845.

Almost surely, 2^645443640 is an apocalyptic number.

645443640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645443640 is an abundant number, since it is smaller than the sum of its proper divisors (1523975040).

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

645443640 is a wasteful number, since it uses less digits than its factorization.

645443640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199234 (or 199221 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 36.

The square root of 645443640 is about 25405.5828510192. The cubic root of 645443640 is about 864.2103076008.

The spelling of 645443640 in words is "six hundred forty-five million, four hundred forty-three thousand, six hundred forty".