217564081 has 24 divisors (see below), whose sum is σ = 262192896. Its totient is φ = 176662080.

The previous prime is 217564073. The next prime is 217564091. The reversal of 217564081 is 180465712.

It is not a de Polignac number, because 217564081 - 2³ = 217564073 is a prime.

It is a super-2 number, since 2×217564081² = 94668258682749122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (217564001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1713040 + ... + 1713166.

It is an arithmetic number, because the mean of its divisors is an integer number (10924704).

Almost surely, 2^217564081 is an apocalyptic number.

It is an amenable number.

217564081 is a deficient number, since it is larger than the sum of its proper divisors (44628815).

217564081 is an equidigital number, since it uses as much as digits as its factorization.

217564081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 349 (or 222 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 217564081 is about 14750.0535931230. The cubic root of 217564081 is about 601.4447415590. Note that the first 3 decimals are identical.

The spelling of 217564081 in words is "two hundred seventeen million, five hundred sixty-four thousand, eighty-one".