81805943 has 2 divisors, whose sum is σ = 81805944. Its totient is φ = 81805942.

The previous prime is 81805939. The next prime is 81805967. The reversal of 81805943 is 34950818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81805943 - 2² = 81805939 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 81805897 and 81805906.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81805903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40902971 + 40902972.

It is an arithmetic number, because the mean of its divisors is an integer number (40902972).

Almost surely, 2^81805943 is an apocalyptic number.

81805943 is a deficient number, since it is larger than the sum of its proper divisors (1).

81805943 is an equidigital number, since it uses as much as digits as its factorization.

81805943 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 38.

The square root of 81805943 is about 9044.6637859016. The cubic root of 81805943 is about 434.1051636255.

The spelling of 81805943 in words is "eighty-one million, eight hundred five thousand, nine hundred forty-three".