2120821 has 4 divisors (see below), whose sum is σ = 2125152. Its totient is φ = 2116492.

The previous prime is 2120819. The next prime is 2120827. The reversal of 2120821 is 1280212.

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 2120821 - 2¹ = 2120819 is a prime.

It is a Duffinian number.

2120821 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 2120795 and 2120804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2120827) 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, 1321 + ... + 2446.

It is an arithmetic number, because the mean of its divisors is an integer number (531288).

2^2120821 is an apocalyptic number.

It is an amenable number.

2120821 is a deficient number, since it is larger than the sum of its proper divisors (4331).

2120821 is an equidigital number, since it uses as much as digits as its factorization.

2120821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4330.

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 2120821 is about 1456.3038831233. The cubic root of 2120821 is about 128.4797466906.

The spelling of 2120821 in words is "two million, one hundred twenty thousand, eight hundred twenty-one".