165221281 has 2 divisors, whose sum is σ = 165221282. Its totient is φ = 165221280.

The previous prime is 165221257. The next prime is 165221293. The reversal of 165221281 is 182122561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 156125025 + 9096256 = 12495^2 + 3016^2 .

It is an emirp because it is prime and its reverse (182122561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 165221281 - 2¹¹ = 165219233 is a prime.

It is a super-2 number, since 2×165221281² = 54596143390561922, which contains 22 as substring.

It is equal to p_9250624 and since 165221281 and 9250624 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (165221681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82610640 + 82610641.

It is an arithmetic number, because the mean of its divisors is an integer number (82610641).

Almost surely, 2^165221281 is an apocalyptic number.

It is an amenable number.

165221281 is a deficient number, since it is larger than the sum of its proper divisors (1).

165221281 is an equidigital number, since it uses as much as digits as its factorization.

165221281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 28.

The square root of 165221281 is about 12853.8430440083. The cubic root of 165221281 is about 548.7257342992.

The spelling of 165221281 in words is "one hundred sixty-five million, two hundred twenty-one thousand, two hundred eighty-one".