165621317 has 2 divisors, whose sum is σ = 165621318. Its totient is φ = 165621316.

The previous prime is 165621311. The next prime is 165621329. The reversal of 165621317 is 713126561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 163686436 + 1934881 = 12794^2 + 1391^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-165621317 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165621311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82810658 + 82810659.

It is an arithmetic number, because the mean of its divisors is an integer number (82810659).

Almost surely, 2^165621317 is an apocalyptic number.

It is an amenable number.

165621317 is a deficient number, since it is larger than the sum of its proper divisors (1).

165621317 is an equidigital number, since it uses as much as digits as its factorization.

165621317 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7560, while the sum is 32.

The square root of 165621317 is about 12869.3945856050. The cubic root of 165621317 is about 549.1682380820.

Adding to 165621317 its reverse (713126561), we get a palindrome (878747878).

The spelling of 165621317 in words is "one hundred sixty-five million, six hundred twenty-one thousand, three hundred seventeen".