165621553 has 2 divisors, whose sum is σ = 165621554. Its totient is φ = 165621552.

The previous prime is 165621457. The next prime is 165621557. The reversal of 165621553 is 355126561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 88040689 + 77580864 = 9383^2 + 8808^2 .

It is a cyclic number.

It is not a de Polignac number, because 165621553 - 2⁹ = 165621041 is a prime.

It is not a weakly prime, because it can be changed into another prime (165621557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82810776 + 82810777.

It is an arithmetic number, because the mean of its divisors is an integer number (82810777).

Almost surely, 2^165621553 is an apocalyptic number.

It is an amenable number.

165621553 is a deficient number, since it is larger than the sum of its proper divisors (1).

165621553 is an equidigital number, since it uses as much as digits as its factorization.

165621553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27000, while the sum is 34.

The square root of 165621553 is about 12869.4037546422. The cubic root of 165621553 is about 549.1684989253.

The spelling of 165621553 in words is "one hundred sixty-five million, six hundred twenty-one thousand, five hundred fifty-three".