645666 has 16 divisors (see below), whose sum is σ = 1475904. Its totient is φ = 184464.

The previous prime is 645661. The next prime is 645683. The reversal of 645666 is 666546.

It is not an unprimeable number, because it can be changed into a prime (645661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7645 + ... + 7728.

It is an arithmetic number, because the mean of its divisors is an integer number (92244).

2⁶⁴⁵⁶⁶⁶ is an apocalyptic number.

645666 is an abundant number, since it is smaller than the sum of its proper divisors (830238).

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

645666 is a wasteful number, since it uses less digits than its factorization.

645666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15385.

The product of its digits is 25920, while the sum is 33.

The square root of 645666 is about 803.5334467214. The cubic root of 645666 is about 86.4309538439.

The spelling of 645666 in words is "six hundred forty-five thousand, six hundred sixty-six".