645537708666 has 48 divisors (see below), whose sum is σ = 1407033805320. Its totient is φ = 213892237440.

The previous prime is 645537708653. The next prime is 645537708713. The reversal of 645537708666 is 666807735546.

It can be written as a sum of positive squares in 4 ways, for example, as 613629389025 + 31908319641 = 783345^2 + 178629^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17859420 + ... + 17895528.

Almost surely, 2^645537708666 is an apocalyptic number.

645537708666 is an abundant number, since it is smaller than the sum of its proper divisors (761496096654).

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

645537708666 is a wasteful number, since it uses less digits than its factorization.

645537708666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42031 (or 42028 counting only the distinct ones).

The product of its (nonzero) digits is 152409600, while the sum is 63.

The spelling of 645537708666 in words is "six hundred forty-five billion, five hundred thirty-seven million, seven hundred eight thousand, six hundred sixty-six".