645988698 has 48 divisors (see below), whose sum is σ = 1464672456. Its totient is φ = 205545600.

The previous prime is 645988687. The next prime is 645988703. The reversal of 645988698 is 896889546.

It can be written as a sum of positive squares in 4 ways, for example, as 554461209 + 91527489 = 23547^2 + 9567^2 .

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, 26148 + ... + 44448.

Almost surely, 2^645988698 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645988698, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (732336228).

645988698 is an abundant number, since it is smaller than the sum of its proper divisors (818683758).

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

645988698 is a wasteful number, since it uses less digits than its factorization.

645988698 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18399 (or 18396 counting only the distinct ones).

The product of its digits is 29859840, while the sum is 63.

The square root of 645988698 is about 25416.3077176839. The cubic root of 645988698 is about 864.4535058087.

The spelling of 645988698 in words is "six hundred forty-five million, nine hundred eighty-eight thousand, six hundred ninety-eight".