645556 has 12 divisors (see below), whose sum is σ = 1136800. Its totient is φ = 320760.

The previous prime is 645529. The next prime is 645571. The reversal of 645556 is 655546.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a nialpdrome in base 15.

It is a congruent number.

It is an unprimeable 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, 391 + ... + 1201.

2⁶⁴⁵⁵⁵⁶ is an apocalyptic number.

It is an amenable number.

645556 is a deficient number, since it is larger than the sum of its proper divisors (491244).

645556 is a wasteful number, since it uses less digits than its factorization.

645556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1014 (or 1012 counting only the distinct ones).

The product of its digits is 18000, while the sum is 31.

The square root of 645556 is about 803.4649961262. The cubic root of 645556 is about 86.4260452457.

The spelling of 645556 in words is "six hundred forty-five thousand, five hundred fifty-six".