216021 has 16 divisors (see below), whose sum is σ = 322560. Its totient is φ = 127680.

The previous prime is 215983. The next prime is 216023. The reversal of 216021 is 120612.

It is not a de Polignac number, because 216021 - 2⁷ = 215893 is a prime.

It is a Curzon number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 215988 and 216006.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 216021.

It is not an unprimeable number, because it can be changed into a prime (216023) 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 15 ways as a sum of consecutive naturals, for example, 1036 + ... + 1226.

It is an arithmetic number, because the mean of its divisors is an integer number (20160).

216021 is a Friedman number, since it can be written as 60^(2+1)+21, using all its digits and the basic arithmetic operations.

2²¹⁶⁰²¹ is an apocalyptic number.

It is an amenable number.

216021 is a deficient number, since it is larger than the sum of its proper divisors (106539).

216021 is a wasteful number, since it uses less digits than its factorization.

216021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 236.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 216021 is about 464.7805933986. The cubic root of 216021 is about 60.0019443814.

Adding to 216021 its reverse (120612), we get a palindrome (336633).

The spelling of 216021 in words is "two hundred sixteen thousand, twenty-one".