645569 has 8 divisors (see below), whose sum is σ = 677160. Its totient is φ = 614656.

The previous prime is 645529. The next prime is 645571. The reversal of 645569 is 965546.

It is a happy number.

645569 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 4 ways, for example, as 97969 + 547600 = 313^2 + 740^2 .

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

It is a 4-Lehmer number, since φ(645569) divides (645569-1)⁴.

It is a cyclic number.

It is not a de Polignac number, because 645569 - 2⁸ = 645313 is a prime.

It is a super-2 number, since 2×645569² = 833518667522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645529) 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, 3179 + ... + 3375.

It is an arithmetic number, because the mean of its divisors is an integer number (84645).

2⁶⁴⁵⁵⁶⁹ is an apocalyptic number.

It is an amenable number.

645569 is a deficient number, since it is larger than the sum of its proper divisors (31591).

645569 is a wasteful number, since it uses less digits than its factorization.

645569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339.

The product of its digits is 32400, while the sum is 35.

The square root of 645569 is about 803.4730860458. The cubic root of 645569 is about 86.4266253818.

The spelling of 645569 in words is "six hundred forty-five thousand, five hundred sixty-nine".