120821 has 4 divisors (see below), whose sum is σ = 127200. Its totient is φ = 114444.

The previous prime is 120817. The next prime is 120823. The reversal of 120821 is 128021.

120821 = 15² + 16² + ... + 71².

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 120821 - 2² = 120817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 120796 and 120805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (120823) 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 3 ways as a sum of consecutive naturals, for example, 3161 + ... + 3198.

It is an arithmetic number, because the mean of its divisors is an integer number (31800).

2¹²⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

120821 is a deficient number, since it is larger than the sum of its proper divisors (6379).

120821 is an equidigital number, since it uses as much as digits as its factorization.

120821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6378.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 120821 is about 347.5931529820. The cubic root of 120821 is about 49.4364725981.

Adding to 120821 its reverse (128021), we get a palindrome (248842).

The spelling of 120821 in words is "one hundred twenty thousand, eight hundred twenty-one".