665557 has 2 divisors, whose sum is σ = 665558. Its totient is φ = 665556.

The previous prime is 665549. The next prime is 665563. The reversal of 665557 is 755566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 579121 + 86436 = 761^2 + 294^2 .

It is a cyclic number.

It is not a de Polignac number, because 665557 - 2³ = 665549 is a prime.

It is a super-2 number, since 2×665557² = 885932240498, which contains 22 as substring.

It is a plaindrome in base 14.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332778 + 332779.

It is an arithmetic number, because the mean of its divisors is an integer number (332779).

2⁶⁶⁵⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

665557 is a deficient number, since it is larger than the sum of its proper divisors (1).

665557 is an equidigital number, since it uses as much as digits as its factorization.

665557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31500, while the sum is 34.

The square root of 665557 is about 815.8167686435. The cubic root of 665557 is about 87.3095504003.

Subtracting 665557 from its reverse (755566), we obtain a palindrome (90009).

The spelling of 665557 in words is "six hundred sixty-five thousand, five hundred fifty-seven".