2121721 has 8 divisors (see below), whose sum is σ = 2476800. Its totient is φ = 1779648.

The previous prime is 2121683. The next prime is 2121737. The reversal of 2121721 is 1271212.

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

It is a cyclic number.

It is not a de Polignac number, because 2121721 - 2¹¹ = 2119673 is a prime.

It is a Duffinian number.

2121721 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 2121695 and 2121704.

It is not an unprimeable number, because it can be changed into a prime (2121751) 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, 2896 + ... + 3553.

It is an arithmetic number, because the mean of its divisors is an integer number (309600).

2^2121721 is an apocalyptic number.

It is an amenable number.

2121721 is a deficient number, since it is larger than the sum of its proper divisors (355079).

2121721 is an equidigital number, since it uses as much as digits as its factorization.

2121721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6503.

The product of its digits is 56, while the sum is 16.

The square root of 2121721 is about 1456.6128517901. The cubic root of 2121721 is about 128.4979181785.

Adding to 2121721 its reverse (1271212), we get a palindrome (3392933).

The spelling of 2121721 in words is "two million, one hundred twenty-one thousand, seven hundred twenty-one".