81954940517 has 2 divisors, whose sum is σ = 81954940518. Its totient is φ = 81954940516.

The previous prime is 81954940477. The next prime is 81954940519. The reversal of 81954940517 is 71504945918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 75639300676 + 6315639841 = 275026^2 + 79471^2 .

It is a cyclic number.

It is not a de Polignac number, because 81954940517 - 2⁶ = 81954940453 is a prime.

It is a super-2 number, since 2×81954940517² (a number of 23 digits) contains 22 as substring.

Together with 81954940519, 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 (81954940519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40977470258 + 40977470259.

It is an arithmetic number, because the mean of its divisors is an integer number (40977470259).

Almost surely, 2^81954940517 is an apocalyptic number.

It is an amenable number.

81954940517 is a deficient number, since it is larger than the sum of its proper divisors (1).

81954940517 is an equidigital number, since it uses as much as digits as its factorization.

81954940517 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1814400, while the sum is 53.

The spelling of 81954940517 in words is "eighty-one billion, nine hundred fifty-four million, nine hundred forty thousand, five hundred seventeen".