81944521 has 2 divisors, whose sum is σ = 81944522. Its totient is φ = 81944520.

The previous prime is 81944509. The next prime is 81944543. The reversal of 81944521 is 12544918.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81812025 + 132496 = 9045^2 + 364^2 .

It is a cyclic number.

It is not a de Polignac number, because 81944521 - 2¹¹ = 81942473 is a prime.

It is not a weakly prime, because it can be changed into another prime (81941521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40972260 + 40972261.

It is an arithmetic number, because the mean of its divisors is an integer number (40972261).

Almost surely, 2^81944521 is an apocalyptic number.

It is an amenable number.

81944521 is a deficient number, since it is larger than the sum of its proper divisors (1).

81944521 is an equidigital number, since it uses as much as digits as its factorization.

81944521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11520, while the sum is 34.

The square root of 81944521 is about 9052.3213045053. The cubic root of 81944521 is about 434.3501478182.

The spelling of 81944521 in words is "eighty-one million, nine hundred forty-four thousand, five hundred twenty-one".