665761 has 2 divisors, whose sum is σ = 665762. Its totient is φ = 665760.

The previous prime is 665747. The next prime is 665773. The reversal of 665761 is 167566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 553536 + 112225 = 744^2 + 335^2 .

It is a cyclic number.

It is not a de Polignac number, because 665761 - 2⁷ = 665633 is a prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (668761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332880 + 332881.

It is an arithmetic number, because the mean of its divisors is an integer number (332881).

2⁶⁶⁵⁷⁶¹ is an apocalyptic number.

It is an amenable number.

665761 is a deficient number, since it is larger than the sum of its proper divisors (1).

665761 is an equidigital number, since it uses as much as digits as its factorization.

665761 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7560, while the sum is 31.

The square root of 665761 is about 815.9417871393. The cubic root of 665761 is about 87.3184699113.

The spelling of 665761 in words is "six hundred sixty-five thousand, seven hundred sixty-one".