81989771 has 2 divisors, whose sum is σ = 81989772. Its totient is φ = 81989770.

The previous prime is 81989767. The next prime is 81989801. The reversal of 81989771 is 17798918.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81989771 - 2² = 81989767 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81989701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40994885 + 40994886.

It is an arithmetic number, because the mean of its divisors is an integer number (40994886).

Almost surely, 2^81989771 is an apocalyptic number.

81989771 is a deficient number, since it is larger than the sum of its proper divisors (1).

81989771 is an equidigital number, since it uses as much as digits as its factorization.

81989771 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 254016, while the sum is 50.

The square root of 81989771 is about 9054.8203184823. The cubic root of 81989771 is about 434.4300829065.

The spelling of 81989771 in words is "eighty-one million, nine hundred eighty-nine thousand, seven hundred seventy-one".