645555 has 8 divisors (see below), whose sum is σ = 1032912. Its totient is φ = 344288.

The previous prime is 645529. The next prime is 645571. The reversal of 645555 is 555546.

645555 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 645555 - 2¹⁰ = 644531 is a prime.

645555 is strictly pandigital in base 7.

It is a nialpdrome in base 15.

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, 21504 + ... + 21533.

It is an arithmetic number, because the mean of its divisors is an integer number (129114).

2⁶⁴⁵⁵⁵⁵ is an apocalyptic number.

645555 is a deficient number, since it is larger than the sum of its proper divisors (387357).

645555 is a wasteful number, since it uses less digits than its factorization.

645555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43045.

The product of its digits is 15000, while the sum is 30.

The square root of 645555 is about 803.4643738213. The cubic root of 645555 is about 86.4260006196.

Subtracting from 645555 its reverse (555546), we obtain a palindrome (90009).

The spelling of 645555 in words is "six hundred forty-five thousand, five hundred fifty-five".