645669 has 6 divisors (see below), whose sum is σ = 932646. Its totient is φ = 430440.

The previous prime is 645661. The next prime is 645683. The reversal of 645669 is 966546.

It is a happy number.

645669 is a `hidden beast` number, since 645 + 6 + 6 + 9 = 666.

645669 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 580644 + 65025 = 762^2 + 255^2 .

It is not a de Polignac number, because 645669 - 2³ = 645661 is a prime.

It is a super-2 number, since 2×645669² = 833776915122, which contains 22 as substring.

It is a congruent number.

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 5 ways as a sum of consecutive naturals, for example, 35862 + ... + 35879.

It is an arithmetic number, because the mean of its divisors is an integer number (155441).

2⁶⁴⁵⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

645669 is a deficient number, since it is larger than the sum of its proper divisors (286977).

645669 is a wasteful number, since it uses less digits than its factorization.

645669 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71747 (or 71744 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 645669 is about 803.5353134741. The cubic root of 645669 is about 86.4310877070.

The spelling of 645669 in words is "six hundred forty-five thousand, six hundred sixty-nine".