216831 has 4 divisors (see below), whose sum is σ = 289112. Its totient is φ = 144552.

The previous prime is 216829. The next prime is 216841. The reversal of 216831 is 138612.

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

It is not a de Polignac number, because 216831 - 2¹ = 216829 is a prime.

It is a super-2 number, since 2×216831² = 94031365122, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

216831 is a lucky number.

It is a plaindrome in base 11 and base 16.

It is a junction number, because it is equal to n+sod(n) for n = 216798 and 216807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36136 + ... + 36141.

It is an arithmetic number, because the mean of its divisors is an integer number (72278).

2²¹⁶⁸³¹ is an apocalyptic number.

216831 is a deficient number, since it is larger than the sum of its proper divisors (72281).

216831 is an equidigital number, since it uses as much as digits as its factorization.

216831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72280.

The product of its digits is 288, while the sum is 21.

The square root of 216831 is about 465.6511569834. The cubic root of 216831 is about 60.0768459807.

The spelling of 216831 in words is "two hundred sixteen thousand, eight hundred thirty-one".