161218261 has 2 divisors, whose sum is σ = 161218262. Its totient is φ = 161218260.

The previous prime is 161218241. The next prime is 161218289. The reversal of 161218261 is 162812161.

It is an a-pointer prime, because the next prime (161218289) can be obtained adding 161218261 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 98903025 + 62315236 = 9945^2 + 7894^2 .

It is an emirp because it is prime and its reverse (162812161) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 161218261 - 2⁵ = 161218229 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161218231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80609130 + 80609131.

It is an arithmetic number, because the mean of its divisors is an integer number (80609131).

Almost surely, 2^161218261 is an apocalyptic number.

It is an amenable number.

161218261 is a deficient number, since it is larger than the sum of its proper divisors (1).

161218261 is an equidigital number, since it uses as much as digits as its factorization.

161218261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1152, while the sum is 28.

The square root of 161218261 is about 12697.1753157937. The cubic root of 161218261 is about 544.2579030961.

The spelling of 161218261 in words is "one hundred sixty-one million, two hundred eighteen thousand, two hundred sixty-one".