165623221 has 2 divisors, whose sum is σ = 165623222. Its totient is φ = 165623220.

The previous prime is 165623201. The next prime is 165623243. The reversal of 165623221 is 122326561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 151560721 + 14062500 = 12311^2 + 3750^2 .

It is a cyclic number.

It is not a de Polignac number, because 165623221 - 2⁵ = 165623189 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 165623221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165623201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82811610 + 82811611.

It is an arithmetic number, because the mean of its divisors is an integer number (82811611).

Almost surely, 2^165623221 is an apocalyptic number.

It is an amenable number.

165623221 is a deficient number, since it is larger than the sum of its proper divisors (1).

165623221 is an equidigital number, since it uses as much as digits as its factorization.

165623221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 28.

The square root of 165623221 is about 12869.4685593462. The cubic root of 165623221 is about 549.1703425058.

Adding to 165623221 its reverse (122326561), we get a palindrome (287949782).

The spelling of 165623221 in words is "one hundred sixty-five million, six hundred twenty-three thousand, two hundred twenty-one".