81121996819 has 2 divisors, whose sum is σ = 81121996820. Its totient is φ = 81121996818.

The previous prime is 81121996793. The next prime is 81121996829. The reversal of 81121996819 is 91869912118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81121996819 - 2²³ = 81113608211 is a prime.

It is a super-2 number, since 2×81121996819² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81121996819.

It is not a weakly prime, because it can be changed into another prime (81121996829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40560998409 + 40560998410.

It is an arithmetic number, because the mean of its divisors is an integer number (40560998410).

Almost surely, 2^81121996819 is an apocalyptic number.

81121996819 is a deficient number, since it is larger than the sum of its proper divisors (1).

81121996819 is an equidigital number, since it uses as much as digits as its factorization.

81121996819 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 559872, while the sum is 55.

The spelling of 81121996819 in words is "eighty-one billion, one hundred twenty-one million, nine hundred ninety-six thousand, eight hundred nineteen".