216686691 has 16 divisors (see below), whose sum is σ = 345711520. Its totient is φ = 133345440.

The previous prime is 216686669. The next prime is 216686711. The reversal of 216686691 is 196686612.

It is not a de Polignac number, because 216686691 - 2⁶ = 216686627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216686791) 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 15 ways as a sum of consecutive naturals, for example, 308320 + ... + 309021.

It is an arithmetic number, because the mean of its divisors is an integer number (21606970).

Almost surely, 2^216686691 is an apocalyptic number.

216686691 is a deficient number, since it is larger than the sum of its proper divisors (129024829).

216686691 is a wasteful number, since it uses less digits than its factorization.

216686691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 617363 (or 617357 counting only the distinct ones).

The product of its digits is 186624, while the sum is 45.

The square root of 216686691 is about 14720.2816209473. The cubic root of 216686691 is about 600.6351523985.

The spelling of 216686691 in words is "two hundred sixteen million, six hundred eighty-six thousand, six hundred ninety-one".