81911243 has 2 divisors, whose sum is σ = 81911244. Its totient is φ = 81911242.

The previous prime is 81911233. The next prime is 81911251. The reversal of 81911243 is 34211918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81911243 - 2¹⁰ = 81910219 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (81911213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40955621 + 40955622.

It is an arithmetic number, because the mean of its divisors is an integer number (40955622).

Almost surely, 2^81911243 is an apocalyptic number.

81911243 is a deficient number, since it is larger than the sum of its proper divisors (1).

81911243 is an equidigital number, since it uses as much as digits as its factorization.

81911243 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 29.

The square root of 81911243 is about 9050.4830257838. The cubic root of 81911243 is about 434.2913427424.

The spelling of 81911243 in words is "eighty-one million, nine hundred eleven thousand, two hundred forty-three".