645558 has 16 divisors (see below), whose sum is σ = 1367280. Its totient is φ = 202496.

The previous prime is 645529. The next prime is 645571. The reversal of 645558 is 855546.

It is a super-3 number, since 3×645558³ = 807099460539243336, which contains 333 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3063 + ... + 3266.

It is an arithmetic number, because the mean of its divisors is an integer number (85455).

2⁶⁴⁵⁵⁵⁸ is an apocalyptic number.

645558 is an abundant number, since it is smaller than the sum of its proper divisors (721722).

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

645558 is a wasteful number, since it uses less digits than its factorization.

645558 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6351.

The product of its digits is 24000, while the sum is 33.

The square root of 645558 is about 803.4662407345. The cubic root of 645558 is about 86.4261344979.

The spelling of 645558 in words is "six hundred forty-five thousand, five hundred fifty-eight".