811721843 has 2 divisors, whose sum is σ = 811721844. Its totient is φ = 811721842.

The previous prime is 811721839. The next prime is 811721851. The reversal of 811721843 is 348127118.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 811721843 - 2² = 811721839 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (811721863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 405860921 + 405860922.

It is an arithmetic number, because the mean of its divisors is an integer number (405860922).

Almost surely, 2^811721843 is an apocalyptic number.

811721843 is a deficient number, since it is larger than the sum of its proper divisors (1).

811721843 is an equidigital number, since it uses as much as digits as its factorization.

811721843 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10752, while the sum is 35.

The square root of 811721843 is about 28490.7325809639. The cubic root of 811721843 is about 932.8297987002.

The spelling of 811721843 in words is "eight hundred eleven million, seven hundred twenty-one thousand, eight hundred forty-three".