216811661 has 8 divisors (see below), whose sum is σ = 236881344. Its totient is φ = 196801920.

The previous prime is 216811643. The next prime is 216811663. The reversal of 216811661 is 166118612.

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

It is a cyclic number.

It is not a de Polignac number, because 216811661 - 2⁶ = 216811597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216811663) 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, 7241 + ... + 22046.

It is an arithmetic number, because the mean of its divisors is an integer number (29610168).

Almost surely, 2^216811661 is an apocalyptic number.

It is an amenable number.

216811661 is a deficient number, since it is larger than the sum of its proper divisors (20069683).

216811661 is a wasteful number, since it uses less digits than its factorization.

216811661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29971.

The product of its digits is 3456, while the sum is 32.

The square root of 216811661 is about 14724.5258327730. The cubic root of 216811661 is about 600.7505985744.

The spelling of 216811661 in words is "two hundred sixteen million, eight hundred eleven thousand, six hundred sixty-one".