216818681 has 4 divisors (see below), whose sum is σ = 223812864. Its totient is φ = 209824500.

The previous prime is 216818669. The next prime is 216818717. The reversal of 216818681 is 186818612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216818681 - 2⁶ = 216818617 is a prime.

It is a super-2 number, since 2×216818681² = 94020680861159522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216818611) 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 3 ways as a sum of consecutive naturals, for example, 3497045 + ... + 3497106.

It is an arithmetic number, because the mean of its divisors is an integer number (55953216).

Almost surely, 2^216818681 is an apocalyptic number.

It is an amenable number.

216818681 is a deficient number, since it is larger than the sum of its proper divisors (6994183).

216818681 is an equidigital number, since it uses as much as digits as its factorization.

216818681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6994182.

The product of its digits is 36864, while the sum is 41.

The square root of 216818681 is about 14724.7642086385. The cubic root of 216818681 is about 600.7570822719.

The spelling of 216818681 in words is "two hundred sixteen million, eight hundred eighteen thousand, six hundred eighty-one".