81821449847 has 2 divisors, whose sum is σ = 81821449848. Its totient is φ = 81821449846.

The previous prime is 81821449819. The next prime is 81821449849. The reversal of 81821449847 is 74894412818.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81821449847 - 2⁶ = 81821449783 is a prime.

Together with 81821449849, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81821449792 and 81821449801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81821449849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40910724923 + 40910724924.

It is an arithmetic number, because the mean of its divisors is an integer number (40910724924).

Almost surely, 2^81821449847 is an apocalyptic number.

81821449847 is a deficient number, since it is larger than the sum of its proper divisors (1).

81821449847 is an equidigital number, since it uses as much as digits as its factorization.

81821449847 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4128768, while the sum is 56.

The spelling of 81821449847 in words is "eighty-one billion, eight hundred twenty-one million, four hundred forty-nine thousand, eight hundred forty-seven".