665381 has 2 divisors, whose sum is σ = 665382. Its totient is φ = 665380.

The previous prime is 665369. The next prime is 665387. The reversal of 665381 is 183566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 664225 + 1156 = 815^2 + 34^2 .

It is a cyclic number.

It is not a de Polignac number, because 665381 - 2¹⁰ = 664357 is a prime.

It is a super-2 number, since 2×665381² = 885463750322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332690 + 332691.

It is an arithmetic number, because the mean of its divisors is an integer number (332691).

2⁶⁶⁵³⁸¹ is an apocalyptic number.

It is an amenable number.

665381 is a deficient number, since it is larger than the sum of its proper divisors (1).

665381 is an equidigital number, since it uses as much as digits as its factorization.

665381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 665381 is about 815.7088941528. The cubic root of 665381 is about 87.3018536713.

The spelling of 665381 in words is "six hundred sixty-five thousand, three hundred eighty-one".