81117518 has 4 divisors (see below), whose sum is σ = 121676280. Its totient is φ = 40558758.

The previous prime is 81117499. The next prime is 81117541. The reversal of 81117518 is 81571118.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81571118 = 2 ⋅40785559.

It is a congruent number.

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 as a sum of consecutive naturals, namely, 20279378 + ... + 20279381.

It is an arithmetic number, because the mean of its divisors is an integer number (30419070).

Almost surely, 2^81117518 is an apocalyptic number.

81117518 is a deficient number, since it is larger than the sum of its proper divisors (40558762).

81117518 is a wasteful number, since it uses less digits than its factorization.

81117518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40558761.

The product of its digits is 2240, while the sum is 32.

The square root of 81117518 is about 9006.5264114419. The cubic root of 81117518 is about 432.8840172444.

The spelling of 81117518 in words is "eighty-one million, one hundred seventeen thousand, five hundred eighteen".