2001821 has 4 divisors (see below), whose sum is σ = 2107200. Its totient is φ = 1896444.

The previous prime is 2001809. The next prime is 2001833. The reversal of 2001821 is 1281002.

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 an interprime number because it is at equal distance from previous prime (2001809) and next prime (2001833).

It is a cyclic number.

It is not a de Polignac number, because 2001821 - 2¹⁸ = 1739677 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2001796 and 2001805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2001421) 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, 52661 + ... + 52698.

It is an arithmetic number, because the mean of its divisors is an integer number (526800).

2^2001821 is an apocalyptic number.

It is an amenable number.

2001821 is a deficient number, since it is larger than the sum of its proper divisors (105379).

2001821 is a wasteful number, since it uses less digits than its factorization.

2001821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105378.

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

The square root of 2001821 is about 1414.8572366144. The cubic root of 2001821 is about 126.0303319938.

Adding to 2001821 its reverse (1281002), we get a palindrome (3282823).

The spelling of 2001821 in words is "two million, one thousand, eight hundred twenty-one".