81841789 has 2 divisors, whose sum is σ = 81841790. Its totient is φ = 81841788.

The previous prime is 81841787. The next prime is 81841801. The reversal of 81841789 is 98714818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72539289 + 9302500 = 8517^2 + 3050^2 .

It is a cyclic number.

It is not a de Polignac number, because 81841789 - 2¹ = 81841787 is a prime.

Together with 81841787, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81841783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40920894 + 40920895.

It is an arithmetic number, because the mean of its divisors is an integer number (40920895).

Almost surely, 2^81841789 is an apocalyptic number.

It is an amenable number.

81841789 is a deficient number, since it is larger than the sum of its proper divisors (1).

81841789 is an equidigital number, since it uses as much as digits as its factorization.

81841789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 129024, while the sum is 46.

The square root of 81841789 is about 9046.6451792916. The cubic root of 81841789 is about 434.1685602477.

The spelling of 81841789 in words is "eighty-one million, eight hundred forty-one thousand, seven hundred eighty-nine".