81664441 has 2 divisors, whose sum is σ = 81664442. Its totient is φ = 81664440.

The previous prime is 81664423. The next prime is 81664463. The reversal of 81664441 is 14446618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78499600 + 3164841 = 8860^2 + 1779^2 .

It is a cyclic number.

It is not a de Polignac number, because 81664441 - 2⁹ = 81663929 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81664397 and 81664406.

It is not a weakly prime, because it can be changed into another prime (81664241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40832220 + 40832221.

It is an arithmetic number, because the mean of its divisors is an integer number (40832221).

Almost surely, 2^81664441 is an apocalyptic number.

It is an amenable number.

81664441 is a deficient number, since it is larger than the sum of its proper divisors (1).

81664441 is an equidigital number, since it uses as much as digits as its factorization.

81664441 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18432, while the sum is 34.

The square root of 81664441 is about 9036.8379978840. The cubic root of 81664441 is about 433.8547246074.

The spelling of 81664441 in words is "eighty-one million, six hundred sixty-four thousand, four hundred forty-one".