81699021871 has 2 divisors, whose sum is σ = 81699021872. Its totient is φ = 81699021870.

The previous prime is 81699021869. The next prime is 81699021883. The reversal of 81699021871 is 17812099618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81699021871 - 2¹ = 81699021869 is a prime.

Together with 81699021869, 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 (81699021841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40849510935 + 40849510936.

It is an arithmetic number, because the mean of its divisors is an integer number (40849510936).

Almost surely, 2^81699021871 is an apocalyptic number.

81699021871 is a deficient number, since it is larger than the sum of its proper divisors (1).

81699021871 is an equidigital number, since it uses as much as digits as its factorization.

81699021871 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 435456, while the sum is 52.

The spelling of 81699021871 in words is "eighty-one billion, six hundred ninety-nine million, twenty-one thousand, eight hundred seventy-one".