81317491 has 2 divisors, whose sum is σ = 81317492.
Its totient is φ = 81317490.
The previous prime is 81317461. The next prime is 81317521. The reversal of 81317491 is 19471318.
It is a balanced prime because it is at equal distance from previous prime (81317461) and next prime (81317521).
It is a cyclic number.
It is not a de Polignac number, because 81317491 - 219 = 80793203 is a prime.
It is a super-2 number, since 2×813174912 = 13225068685070162, which contains 22 as substring.
It is not a weakly prime, because it can be changed into another prime (81317441) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40658745 + 40658746.
It is an arithmetic number, because the mean of its divisors is an integer number (40658746).
Almost surely, 281317491 is an apocalyptic number.
81317491 is a deficient number, since it is larger than the sum of its proper divisors (1).
81317491 is an equidigital number, since it uses as much as digits as its factorization.
81317491 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 6048, while the sum is 34.
The square root of 81317491 is about 9017.6211386374.
The cubic root of 81317491 is about 433.2394442873.
The spelling of 81317491 in words is "eighty-one million, three hundred seventeen thousand, four hundred ninety-one".