645566 has 4 divisors (see below), whose sum is σ = 968352. Its totient is φ = 322782.

The previous prime is 645529. The next prime is 645571. The reversal of 645566 is 665546.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161390 + ... + 161393.

It is an arithmetic number, because the mean of its divisors is an integer number (242088).

2⁶⁴⁵⁵⁶⁶ is an apocalyptic number.

645566 is a deficient number, since it is larger than the sum of its proper divisors (322786).

645566 is a wasteful number, since it uses less digits than its factorization.

645566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322785.

The product of its digits is 21600, while the sum is 32.

The square root of 645566 is about 803.4712191485. The cubic root of 645566 is about 86.4264915050.

The spelling of 645566 in words is "six hundred forty-five thousand, five hundred sixty-six".