2102821 has 16 divisors (see below), whose sum is σ = 2582784. Its totient is φ = 1672704.

The previous prime is 2102809. The next prime is 2102831. The reversal of 2102821 is 1282012.

It is a cyclic number.

It is not a de Polignac number, because 2102821 - 2⁷ = 2102693 is a prime.

It is a Duffinian number.

2102821 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 2102795 and 2102804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2102801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5781 + ... + 6133.

It is an arithmetic number, because the mean of its divisors is an integer number (161424).

2^2102821 is an apocalyptic number.

It is an amenable number.

2102821 is a deficient number, since it is larger than the sum of its proper divisors (479963).

2102821 is a wasteful number, since it uses less digits than its factorization.

2102821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420.

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

The square root of 2102821 is about 1450.1106854306. The cubic root of 2102821 is about 128.1152323309.

Adding to 2102821 its reverse (1282012), we get a palindrome (3384833).

The spelling of 2102821 in words is "two million, one hundred two thousand, eight hundred twenty-one".