165215221 has 2 divisors, whose sum is σ = 165215222. Its totient is φ = 165215220.

The previous prime is 165215201. The next prime is 165215251. The reversal of 165215221 is 122512561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 158382225 + 6832996 = 12585^2 + 2614^2 .

It is an emirp because it is prime and its reverse (122512561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 165215221 - 2¹⁷ = 165084149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165215201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82607610 + 82607611.

It is an arithmetic number, because the mean of its divisors is an integer number (82607611).

Almost surely, 2^165215221 is an apocalyptic number.

It is an amenable number.

165215221 is a deficient number, since it is larger than the sum of its proper divisors (1).

165215221 is an equidigital number, since it uses as much as digits as its factorization.

165215221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1200, while the sum is 25.

The square root of 165215221 is about 12853.6073146802. The cubic root of 165215221 is about 548.7190254810.

Adding to 165215221 its reverse (122512561), we get a palindrome (287727782).

The spelling of 165215221 in words is "one hundred sixty-five million, two hundred fifteen thousand, two hundred twenty-one".