81517281 has 8 divisors (see below), whose sum is σ = 108749280. Its totient is φ = 54315072.

The previous prime is 81517279. The next prime is 81517283. The reversal of 81517281 is 18271518.

It is an interprime number because it is at equal distance from previous prime (81517279) and next prime (81517283).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81517281 - 2¹ = 81517279 is a prime.

It is a super-2 number, since 2×81517281² = 13290134203265922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81517283) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6 + ... + 12768.

It is an arithmetic number, because the mean of its divisors is an integer number (13593660).

Almost surely, 2^81517281 is an apocalyptic number.

It is an amenable number.

81517281 is a deficient number, since it is larger than the sum of its proper divisors (27231999).

81517281 is a wasteful number, since it uses less digits than its factorization.

81517281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14895.

The product of its digits is 4480, while the sum is 33.

The square root of 81517281 is about 9028.6920979730. The cubic root of 81517281 is about 433.5939646433.

Adding to 81517281 its reverse (18271518), we get a palindrome (99788799).

The spelling of 81517281 in words is "eighty-one million, five hundred seventeen thousand, two hundred eighty-one".