81535217 has 2 divisors, whose sum is σ = 81535218. Its totient is φ = 81535216.

The previous prime is 81535187. The next prime is 81535219. The reversal of 81535217 is 71253518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79995136 + 1540081 = 8944^2 + 1241^2 .

It is a cyclic number.

It is not a de Polignac number, because 81535217 - 2⁸ = 81534961 is a prime.

It is a super-2 number, since 2×81535217² = 13295983222474178, which contains 22 as substring.

Together with 81535219, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81535219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40767608 + 40767609.

It is an arithmetic number, because the mean of its divisors is an integer number (40767609).

Almost surely, 2^81535217 is an apocalyptic number.

It is an amenable number.

81535217 is a deficient number, since it is larger than the sum of its proper divisors (1).

81535217 is an equidigital number, since it uses as much as digits as its factorization.

81535217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 32.

The square root of 81535217 is about 9029.6853212058. The cubic root of 81535217 is about 433.6257630994.

The spelling of 81535217 in words is "eighty-one million, five hundred thirty-five thousand, two hundred seventeen".