165571561 has 2 divisors, whose sum is σ = 165571562. Its totient is φ = 165571560.

The previous prime is 165571541. The next prime is 165571591. The reversal of 165571561 is 165175561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 158281561 + 7290000 = 12581^2 + 2700^2 .

It is a cyclic number.

It is not a de Polignac number, because 165571561 - 2⁷ = 165571433 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 165571561.

It is not a weakly prime, because it can be changed into another prime (165571501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82785780 + 82785781.

It is an arithmetic number, because the mean of its divisors is an integer number (82785781).

Almost surely, 2^165571561 is an apocalyptic number.

It is an amenable number.

165571561 is a deficient number, since it is larger than the sum of its proper divisors (1).

165571561 is an equidigital number, since it uses as much as digits as its factorization.

165571561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31500, while the sum is 37.

The square root of 165571561 is about 12867.4613269285. The cubic root of 165571561 is about 549.1132388181.

The spelling of 165571561 in words is "one hundred sixty-five million, five hundred seventy-one thousand, five hundred sixty-one".