665569 has 2 divisors, whose sum is σ = 665570. Its totient is φ = 665568.

The previous prime is 665563. The next prime is 665573. The reversal of 665569 is 965566.

It is a happy number.

665569 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 471969 + 193600 = 687^2 + 440^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665569 is a prime.

It is a super-2 number, since 2×665569² = 885964187522, which contains 22 as substring.

665569 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332784 + 332785.

It is an arithmetic number, because the mean of its divisors is an integer number (332785).

2⁶⁶⁵⁵⁶⁹ is an apocalyptic number.

It is an amenable number.

665569 is a deficient number, since it is larger than the sum of its proper divisors (1).

665569 is an equidigital number, since it uses as much as digits as its factorization.

665569 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48600, while the sum is 37.

The square root of 665569 is about 815.8241232030. The cubic root of 665569 is about 87.3100751279.

It can be divided in two parts, 6655 and 69, that added together give a square (6724 = 82²).

The spelling of 665569 in words is "six hundred sixty-five thousand, five hundred sixty-nine".