165421621 has 2 divisors, whose sum is σ = 165421622. Its totient is φ = 165421620.

The previous prime is 165421603. The next prime is 165421687. The reversal of 165421621 is 126124561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 154728721 + 10692900 = 12439^2 + 3270^2 .

It is an emirp because it is prime and its reverse (126124561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 165421621 - 2¹³ = 165413429 is a prime.

It is equal to p_9261109 and since 165421621 and 9261109 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 165421621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165421601) 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, 82710810 + 82710811.

It is an arithmetic number, because the mean of its divisors is an integer number (82710811).

Almost surely, 2^165421621 is an apocalyptic number.

It is an amenable number.

165421621 is a deficient number, since it is larger than the sum of its proper divisors (1).

165421621 is an equidigital number, since it uses as much as digits as its factorization.

165421621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 28.

The square root of 165421621 is about 12861.6336831679. The cubic root of 165421621 is about 548.9474315488.

The spelling of 165421621 in words is "one hundred sixty-five million, four hundred twenty-one thousand, six hundred twenty-one".