216491931 has 24 divisors (see below), whose sum is σ = 331400160. Its totient is φ = 135945600.

The previous prime is 216491929. The next prime is 216491959. The reversal of 216491931 is 139194612.

It is a happy number.

216491931 is a `hidden beast` number, since 2 + 1 + 649 + 1 + 9 + 3 + 1 = 666.

It is not a de Polignac number, because 216491931 - 2¹ = 216491929 is a prime.

It is a super-2 number, since 2×216491931² = 93737512376217522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (216491131) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 586 + ... + 20816.

It is an arithmetic number, because the mean of its divisors is an integer number (13808340).

Almost surely, 2^216491931 is an apocalyptic number.

216491931 is a deficient number, since it is larger than the sum of its proper divisors (114908229).

216491931 is a wasteful number, since it uses less digits than its factorization.

216491931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20307 (or 20304 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 216491931 is about 14713.6647712254. The cubic root of 216491931 is about 600.4551463157.

The spelling of 216491931 in words is "two hundred sixteen million, four hundred ninety-one thousand, nine hundred thirty-one".