81186704981 has 2 divisors, whose sum is σ = 81186704982. Its totient is φ = 81186704980.

The previous prime is 81186704957. The next prime is 81186704983. The reversal of 81186704981 is 18940768118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69045970756 + 12140734225 = 262766^2 + 110185^2 .

It is a cyclic number.

It is not a de Polignac number, because 81186704981 - 2⁶ = 81186704917 is a prime.

It is a super-2 number, since 2×81186704981² (a number of 23 digits) contains 22 as substring.

Together with 81186704983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81186704983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40593352490 + 40593352491.

It is an arithmetic number, because the mean of its divisors is an integer number (40593352491).

Almost surely, 2^81186704981 is an apocalyptic number.

It is an amenable number.

81186704981 is a deficient number, since it is larger than the sum of its proper divisors (1).

81186704981 is an equidigital number, since it uses as much as digits as its factorization.

81186704981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 774144, while the sum is 53.

The spelling of 81186704981 in words is "eighty-one billion, one hundred eighty-six million, seven hundred four thousand, nine hundred eighty-one".