165641321 has 2 divisors, whose sum is σ = 165641322. Its totient is φ = 165641320.

The previous prime is 165641317. The next prime is 165641327. The reversal of 165641321 is 123146561.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 83539600 + 82101721 = 9140^2 + 9061^2 .

It is a cyclic number.

It is not a de Polignac number, because 165641321 - 2² = 165641317 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (165641327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82820660 + 82820661.

It is an arithmetic number, because the mean of its divisors is an integer number (82820661).

Almost surely, 2^165641321 is an apocalyptic number.

It is an amenable number.

165641321 is a deficient number, since it is larger than the sum of its proper divisors (1).

165641321 is an equidigital number, since it uses as much as digits as its factorization.

165641321 is an evil number, because the sum of its binary digits is even.

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

The square root of 165641321 is about 12870.1717548757. The cubic root of 165641321 is about 549.1903469896.

Adding to 165641321 its reverse (123146561), we get a palindrome (288787882).

The spelling of 165641321 in words is "one hundred sixty-five million, six hundred forty-one thousand, three hundred twenty-one".