81722117 has 2 divisors, whose sum is σ = 81722118. Its totient is φ = 81722116.

The previous prime is 81722099. The next prime is 81722119. The reversal of 81722117 is 71122718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78039556 + 3682561 = 8834^2 + 1919^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81722117 is a prime.

Together with 81722119, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81722117.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81722119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40861058 + 40861059.

It is an arithmetic number, because the mean of its divisors is an integer number (40861059).

Almost surely, 2^81722117 is an apocalyptic number.

It is an amenable number.

81722117 is a deficient number, since it is larger than the sum of its proper divisors (1).

81722117 is an equidigital number, since it uses as much as digits as its factorization.

81722117 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1568, while the sum is 29.

The square root of 81722117 is about 9040.0285950875. The cubic root of 81722117 is about 433.9568380700.

The spelling of 81722117 in words is "eighty-one million, seven hundred twenty-two thousand, one hundred seventeen".