81943719691 has 2 divisors, whose sum is σ = 81943719692. Its totient is φ = 81943719690.

The previous prime is 81943719679. The next prime is 81943719713. The reversal of 81943719691 is 19691734918.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81943719691 - 2¹⁹ = 81943195403 is a prime.

It is a super-2 number, since 2×81943719691² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81943719661) 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, 40971859845 + 40971859846.

It is an arithmetic number, because the mean of its divisors is an integer number (40971859846).

Almost surely, 2^81943719691 is an apocalyptic number.

81943719691 is a deficient number, since it is larger than the sum of its proper divisors (1).

81943719691 is an equidigital number, since it uses as much as digits as its factorization.

81943719691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2939328, while the sum is 58.

The spelling of 81943719691 in words is "eighty-one billion, nine hundred forty-three million, seven hundred nineteen thousand, six hundred ninety-one".