217684081 has 2 divisors, whose sum is σ = 217684082. Its totient is φ = 217684080.

The previous prime is 217684079. The next prime is 217684087. The reversal of 217684081 is 180486712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 121330225 + 96353856 = 11015^2 + 9816^2 .

It is a cyclic number.

It is not a de Polignac number, because 217684081 - 2¹ = 217684079 is a prime.

It is a super-2 number, since 2×217684081² = 94772718241629122, which contains 22 as substring.

Together with 217684079, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 217684081.

It is not a weakly prime, because it can be changed into another prime (217684087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108842040 + 108842041.

It is an arithmetic number, because the mean of its divisors is an integer number (108842041).

Almost surely, 2^217684081 is an apocalyptic number.

It is an amenable number.

217684081 is a deficient number, since it is larger than the sum of its proper divisors (1).

217684081 is an equidigital number, since it uses as much as digits as its factorization.

217684081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21504, while the sum is 37.

The square root of 217684081 is about 14754.1208141997. The cubic root of 217684081 is about 601.5552991832. Note that the first 3 decimals are identical.

The spelling of 217684081 in words is "two hundred seventeen million, six hundred eighty-four thousand, eighty-one".