216121 has 4 divisors (see below), whose sum is σ = 228852. Its totient is φ = 203392.

The previous prime is 216119. The next prime is 216127. The reversal of 216121 is 121612.

216121 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in 2 ways, for example, as 189225 + 26896 = 435^2 + 164^2 .

It is a cyclic number.

It is not a de Polignac number, because 216121 - 2¹ = 216119 is a prime.

It is an Ulam number.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216127) 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, 6340 + ... + 6373.

It is an arithmetic number, because the mean of its divisors is an integer number (57213).

2²¹⁶¹²¹ is an apocalyptic number.

It is an amenable number.

216121 is a deficient number, since it is larger than the sum of its proper divisors (12731).

216121 is a wasteful number, since it uses less digits than its factorization.

216121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12730.

The product of its digits is 24, while the sum is 13.

The square root of 216121 is about 464.8881585930. Note that the first 3 decimals coincide. The cubic root of 216121 is about 60.0112016123.

Adding to 216121 its reverse (121612), we get a palindrome (337733).

The spelling of 216121 in words is "two hundred sixteen thousand, one hundred twenty-one".