81722717 has 4 divisors (see below), whose sum is σ = 83715996. Its totient is φ = 79729440.

The previous prime is 81722651. The next prime is 81722777. The reversal of 81722717 is 71722718.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5317636 + 76405081 = 2306^2 + 8741^2 .

It is a cyclic number.

It is not a de Polignac number, because 81722717 - 2⁸ = 81722461 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81722777) 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 in 3 ways as a sum of consecutive naturals, for example, 996578 + ... + 996659.

It is an arithmetic number, because the mean of its divisors is an integer number (20928999).

Almost surely, 2^81722717 is an apocalyptic number.

It is an amenable number.

81722717 is a deficient number, since it is larger than the sum of its proper divisors (1993279).

81722717 is a wasteful number, since it uses less digits than its factorization.

81722717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1993278.

The product of its digits is 10976, while the sum is 35.

The square root of 81722717 is about 9040.0617807623. The cubic root of 81722717 is about 433.9579000977.

Subtracting from 81722717 its reverse (71722718), we obtain a palindrome (9999999).

The spelling of 81722717 in words is "eighty-one million, seven hundred twenty-two thousand, seven hundred seventeen".