81947771 has 2 divisors, whose sum is σ = 81947772. Its totient is φ = 81947770.

The previous prime is 81947753. The next prime is 81947773. The reversal of 81947771 is 17774918.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81947771 - 2²⁶ = 14838907 is a prime.

Together with 81947773, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81947773) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40973885 + 40973886.

It is an arithmetic number, because the mean of its divisors is an integer number (40973886).

Almost surely, 2^81947771 is an apocalyptic number.

81947771 is a deficient number, since it is larger than the sum of its proper divisors (1).

81947771 is an equidigital number, since it uses as much as digits as its factorization.

81947771 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 98784, while the sum is 44.

The square root of 81947771 is about 9052.5008146920. The cubic root of 81947771 is about 434.3558899931.

The spelling of 81947771 in words is "eighty-one million, nine hundred forty-seven thousand, seven hundred seventy-one".