665801 has 2 divisors, whose sum is σ = 665802. Its totient is φ = 665800.

The previous prime is 665789. The next prime is 665803. The reversal of 665801 is 108566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 462400 + 203401 = 680^2 + 451^2 .

It is a cyclic number.

It is not a de Polignac number, because 665801 - 2¹⁰ = 664777 is a prime.

Together with 665803, it forms a pair of twin primes.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 665801.

It is not a weakly prime, because it can be changed into another prime (665803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332900 + 332901.

It is an arithmetic number, because the mean of its divisors is an integer number (332901).

2⁶⁶⁵⁸⁰¹ is an apocalyptic number.

It is an amenable number.

665801 is a deficient number, since it is larger than the sum of its proper divisors (1).

665801 is an equidigital number, since it uses as much as digits as its factorization.

665801 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 665801 is about 815.9662983237. The cubic root of 665801 is about 87.3202186213.

The spelling of 665801 in words is "six hundred sixty-five thousand, eight hundred one".