81612161 has 2 divisors, whose sum is σ = 81612162. Its totient is φ = 81612160.

The previous prime is 81612143. The next prime is 81612187. The reversal of 81612161 is 16121618.

It is an a-pointer prime, because the next prime (81612187) can be obtained adding 81612161 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63600625 + 18011536 = 7975^2 + 4244^2 .

It is a cyclic number.

It is not a de Polignac number, because 81612161 - 2¹⁴ = 81595777 is a prime.

It is a Sophie Germain prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81612161.

It is not a weakly prime, because it can be changed into another prime (81612101) 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, 40806080 + 40806081.

It is an arithmetic number, because the mean of its divisors is an integer number (40806081).

Almost surely, 2^81612161 is an apocalyptic number.

It is an amenable number.

81612161 is a deficient number, since it is larger than the sum of its proper divisors (1).

81612161 is an equidigital number, since it uses as much as digits as its factorization.

81612161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 26.

The square root of 81612161 is about 9033.9449300956. The cubic root of 81612161 is about 433.7621230351.

Adding to 81612161 its reverse (16121618), we get a palindrome (97733779).

The spelling of 81612161 in words is "eighty-one million, six hundred twelve thousand, one hundred sixty-one".