81299287 has 4 divisors (see below), whose sum is σ = 86081616. Its totient is φ = 76516960.

The previous prime is 81299213. The next prime is 81299311. The reversal of 81299287 is 78299218.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81299287 - 2⁷ = 81299159 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81299087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2391139 + ... + 2391172.

It is an arithmetic number, because the mean of its divisors is an integer number (21520404).

Almost surely, 2^81299287 is an apocalyptic number.

81299287 is a deficient number, since it is larger than the sum of its proper divisors (4782329).

81299287 is a wasteful number, since it uses less digits than its factorization.

81299287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4782328.

The product of its digits is 145152, while the sum is 46.

The square root of 81299287 is about 9016.6117250329. The cubic root of 81299287 is about 433.2071130741.

The spelling of 81299287 in words is "eighty-one million, two hundred ninety-nine thousand, two hundred eighty-seven".