81996221 has 2 divisors, whose sum is σ = 81996222. Its totient is φ = 81996220.

The previous prime is 81996203. The next prime is 81996283. The reversal of 81996221 is 12269918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63840100 + 18156121 = 7990^2 + 4261^2 .

It is a cyclic number.

It is not a de Polignac number, because 81996221 - 2¹⁰ = 81995197 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 (81996121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40998110 + 40998111.

It is an arithmetic number, because the mean of its divisors is an integer number (40998111).

Almost surely, 2^81996221 is an apocalyptic number.

It is an amenable number.

81996221 is a deficient number, since it is larger than the sum of its proper divisors (1).

81996221 is an equidigital number, since it uses as much as digits as its factorization.

81996221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 38.

The square root of 81996221 is about 9055.1764753648. The cubic root of 81996221 is about 434.4414745737.

The spelling of 81996221 in words is "eighty-one million, nine hundred ninety-six thousand, two hundred twenty-one".