81308217 has 8 divisors (see below), whose sum is σ = 108925600. Its totient is φ = 53948160.

The previous prime is 81308191. The next prime is 81308221. The reversal of 81308217 is 71280318.

It is a happy number.

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

It is not a de Polignac number, because 81308217 - 2⁷ = 81308089 is a prime.

It is a super-2 number, since 2×81308217² = 13222052303438178, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81308237) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 63592 + ... + 64857.

It is an arithmetic number, because the mean of its divisors is an integer number (13615700).

Almost surely, 2^81308217 is an apocalyptic number.

It is an amenable number.

81308217 is a deficient number, since it is larger than the sum of its proper divisors (27617383).

81308217 is a wasteful number, since it uses less digits than its factorization.

81308217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128663.

The product of its (nonzero) digits is 2688, while the sum is 30.

The square root of 81308217 is about 9017.1069085378. The cubic root of 81308217 is about 433.2229738031. Note that the first 3 decimals are identical.

The spelling of 81308217 in words is "eighty-one million, three hundred eight thousand, two hundred seventeen".