81173545 has 4 divisors (see below), whose sum is σ = 97408260. Its totient is φ = 64938832.

The previous prime is 81173501. The next prime is 81173621. The reversal of 81173545 is 54537118.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54537118 = 2 ⋅27268559.

It can be written as a sum of positive squares in 2 ways, for example, as 11417641 + 69755904 = 3379^2 + 8352^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81173545 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81173545.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8117350 + ... + 8117359.

It is an arithmetic number, because the mean of its divisors is an integer number (24352065).

Almost surely, 2^81173545 is an apocalyptic number.

It is an amenable number.

81173545 is a deficient number, since it is larger than the sum of its proper divisors (16234715).

81173545 is a wasteful number, since it uses less digits than its factorization.

81173545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16234714.

The product of its digits is 16800, while the sum is 34.

The square root of 81173545 is about 9009.6362301705. The cubic root of 81173545 is about 432.9836570911.

It can be divided in two parts, 81173 and 545, that added together give a palindrome (81718).

The spelling of 81173545 in words is "eighty-one million, one hundred seventy-three thousand, five hundred forty-five".