645656640 has 112 divisors (see below), whose sum is σ = 2070567360. Its totient is φ = 170444800.

The previous prime is 645656629. The next prime is 645656677. The reversal of 645656640 is 46656546.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 645656592 and 645656601.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 93631 + ... + 100289.

Almost surely, 2^645656640 is an apocalyptic number.

645656640 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 645656640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1035283680).

645656640 is an abundant number, since it is smaller than the sum of its proper divisors (1424910720).

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

645656640 is a wasteful number, since it uses less digits than its factorization.

645656640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6780 (or 6770 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 42.

The square root of 645656640 is about 25409.7744972284. The cubic root of 645656640 is about 864.3053618855.

The spelling of 645656640 in words is "six hundred forty-five million, six hundred fifty-six thousand, six hundred forty".