81722817 has 16 divisors (see below), whose sum is σ = 132077760. Its totient is φ = 49528800.

The previous prime is 81722813. The next prime is 81722827. The reversal of 81722817 is 71822718.

It is a happy number.

It is not a de Polignac number, because 81722817 - 2² = 81722813 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81722813) 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 in 15 ways as a sum of consecutive naturals, for example, 137284 + ... + 137877.

It is an arithmetic number, because the mean of its divisors is an integer number (8254860).

Almost surely, 2^81722817 is an apocalyptic number.

It is an amenable number.

81722817 is a deficient number, since it is larger than the sum of its proper divisors (50354943).

81722817 is a wasteful number, since it uses less digits than its factorization.

81722817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275181 (or 275175 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 81722817 is about 9040.0673116963. The cubic root of 81722817 is about 433.9580771018.

Subtracting from 81722817 its reverse (71822718), we obtain a palindrome (9900099).

The spelling of 81722817 in words is "eighty-one million, seven hundred twenty-two thousand, eight hundred seventeen".