216491 has 4 divisors (see below), whose sum is σ = 236184. Its totient is φ = 196800.

The previous prime is 216481. The next prime is 216493. The reversal of 216491 is 194612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216491 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 216491.

It is not an unprimeable number, because it can be changed into a prime (216493) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9830 + ... + 9851.

It is an arithmetic number, because the mean of its divisors is an integer number (59046).

2²¹⁶⁴⁹¹ is an apocalyptic number.

216491 is a deficient number, since it is larger than the sum of its proper divisors (19693).

216491 is a wasteful number, since it uses less digits than its factorization.

216491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19692.

The product of its digits is 432, while the sum is 23.

The square root of 216491 is about 465.2859335935. The cubic root of 216491 is about 60.0454285584.

It can be divided in two parts, 216 and 491, that added together give a palindrome (707).

The spelling of 216491 in words is "two hundred sixteen thousand, four hundred ninety-one".