81717745 has 4 divisors (see below), whose sum is σ = 98061300. Its totient is φ = 65374192.

The previous prime is 81717743. The next prime is 81717751. The reversal of 81717745 is 54771718.

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 44836416 + 36881329 = 6696^2 + 6073^2 .

It is a cyclic number.

It is not a de Polignac number, because 81717745 - 2¹ = 81717743 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 81717698 and 81717707.

It is not an unprimeable number, because it can be changed into a prime (81717743) 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 3 ways as a sum of consecutive naturals, for example, 8171770 + ... + 8171779.

It is an arithmetic number, because the mean of its divisors is an integer number (24515325).

Almost surely, 2^81717745 is an apocalyptic number.

It is an amenable number.

81717745 is a deficient number, since it is larger than the sum of its proper divisors (16343555).

81717745 is a wasteful number, since it uses less digits than its factorization.

81717745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16343554.

The product of its digits is 54880, while the sum is 40.

The square root of 81717745 is about 9039.7867784589. The cubic root of 81717745 is about 433.9490992709.

The spelling of 81717745 in words is "eighty-one million, seven hundred seventeen thousand, seven hundred forty-five".