165561397 has 2 divisors, whose sum is σ = 165561398. Its totient is φ = 165561396.

The previous prime is 165561379. The next prime is 165561467. The reversal of 165561397 is 793165561.

It is a happy number.

165561397 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

Together with previous prime (165561379) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 160934596 + 4626801 = 12686^2 + 2151^2 .

It is a cyclic number.

It is not a de Polignac number, because 165561397 - 2¹⁹ = 165037109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165568397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82780698 + 82780699.

It is an arithmetic number, because the mean of its divisors is an integer number (82780699).

Almost surely, 2^165561397 is an apocalyptic number.

It is an amenable number.

165561397 is a deficient number, since it is larger than the sum of its proper divisors (1).

165561397 is an equidigital number, since it uses as much as digits as its factorization.

165561397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 170100, while the sum is 43.

The square root of 165561397 is about 12867.0663711664. The cubic root of 165561397 is about 549.1020023852.

The spelling of 165561397 in words is "one hundred sixty-five million, five hundred sixty-one thousand, three hundred ninety-seven".