2021721 has 8 divisors (see below), whose sum is σ = 2903040. Its totient is φ = 1244112.

The previous prime is 2021711. The next prime is 2021729. The reversal of 2021721 is 1271202.

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

It is a de Polignac number, because none of the positive numbers 2^k-2021721 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 2021721.

It is not an unprimeable number, because it can be changed into a prime (2021729) 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, 25881 + ... + 25958.

It is an arithmetic number, because the mean of its divisors is an integer number (362880).

2^2021721 is an apocalyptic number.

It is an amenable number.

2021721 is a deficient number, since it is larger than the sum of its proper divisors (881319).

2021721 is a wasteful number, since it uses less digits than its factorization.

2021721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51855.

The product of its (nonzero) digits is 56, while the sum is 15.

The square root of 2021721 is about 1421.8723571404. The cubic root of 2021721 is about 126.4465760964.

Adding to 2021721 its reverse (1271202), we get a palindrome (3292923).

The spelling of 2021721 in words is "two million, twenty-one thousand, seven hundred twenty-one".