216783891 has 16 divisors (see below), whose sum is σ = 321882400. Its totient is φ = 144198144.

The previous prime is 216783883. The next prime is 216783923. The reversal of 216783891 is 198387612.

It is not a de Polignac number, because 216783891 - 2³ = 216783883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216783811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3555 + ... + 21123.

It is an arithmetic number, because the mean of its divisors is an integer number (20117650).

Almost surely, 2^216783891 is an apocalyptic number.

216783891 is a deficient number, since it is larger than the sum of its proper divisors (105098509).

216783891 is a wasteful number, since it uses less digits than its factorization.

216783891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18035 (or 18029 counting only the distinct ones).

The product of its digits is 145152, while the sum is 45.

The square root of 216783891 is about 14723.5828180508. The cubic root of 216783891 is about 600.7249487295.

The spelling of 216783891 in words is "two hundred sixteen million, seven hundred eighty-three thousand, eight hundred ninety-one".