645988 has 12 divisors (see below), whose sum is σ = 1292032. Its totient is φ = 276840.

The previous prime is 645979. The next prime is 646003. The reversal of 645988 is 889546.

645988 is an admirable number.

It is a super-3 number, since 3×645988³ = 808713338709210816, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 645988.

It is an unprimeable number.

645988 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11508 + ... + 11563.

2⁶⁴⁵⁹⁸⁸ is an apocalyptic number.

It is an amenable number.

645988 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

645988 is a wasteful number, since it uses less digits than its factorization.

645988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23082 (or 23080 counting only the distinct ones).

The product of its digits is 69120, while the sum is 40.

The square root of 645988 is about 803.7337867727. The cubic root of 645988 is about 86.4453194457.

The spelling of 645988 in words is "six hundred forty-five thousand, nine hundred eighty-eight".