81319285 has 4 divisors (see below), whose sum is σ = 97583148. Its totient is φ = 65055424.

The previous prime is 81319267. The next prime is 81319289. The reversal of 81319285 is 58291318.

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 28291761 + 53027524 = 5319^2 + 7282^2 .

It is a cyclic number.

It is not a de Polignac number, because 81319285 - 2⁵ = 81319253 is a prime.

It is a super-2 number, since 2×81319285² = 13225652225822450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81319289) 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, 8131924 + ... + 8131933.

It is an arithmetic number, because the mean of its divisors is an integer number (24395787).

Almost surely, 2^81319285 is an apocalyptic number.

It is an amenable number.

81319285 is a deficient number, since it is larger than the sum of its proper divisors (16263863).

81319285 is a wasteful number, since it uses less digits than its factorization.

81319285 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16263862.

The product of its digits is 17280, while the sum is 37.

The square root of 81319285 is about 9017.7206099990. The cubic root of 81319285 is about 433.2426302597.

The spelling of 81319285 in words is "eighty-one million, three hundred nineteen thousand, two hundred eighty-five".