121821 has 8 divisors (see below), whose sum is σ = 185664. Its totient is φ = 69600.

The previous prime is 121789. The next prime is 121843. The reversal of 121821 is 128121.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 121821 - 2⁵ = 121789 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 121821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2880 + ... + 2921.

It is an arithmetic number, because the mean of its divisors is an integer number (23208).

2¹²¹⁸²¹ is an apocalyptic number.

It is an amenable number.

121821 is a deficient number, since it is larger than the sum of its proper divisors (63843).

121821 is an equidigital number, since it uses as much as digits as its factorization.

121821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5811.

The product of its digits is 32, while the sum is 15.

The square root of 121821 is about 349.0286521190. The cubic root of 121821 is about 49.5724884284.

Adding to 121821 its reverse (128121), we get a palindrome (249942).

The spelling of 121821 in words is "one hundred twenty-one thousand, eight hundred twenty-one".