2721 has 4 divisors (see below), whose sum is σ = 3632. Its totient is φ = 1812.

The previous prime is 2719. The next prime is 2729. The reversal of 2721 is 1272.

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 not a de Polignac number, because 2721 - 2¹ = 2719 is a prime.

It is an Ulam number.

It is a D-number.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 14 and base 16.

It is a junction number, because it is equal to n+sod(n) for n = 2697 and 2706.

It is not an unprimeable number, because it can be changed into a prime (2729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 451 + ... + 456.

It is an arithmetic number, because the mean of its divisors is an integer number (908).

2²⁷²¹ is an apocalyptic number.

It is an amenable number.

2721 is a deficient number, since it is larger than the sum of its proper divisors (911).

2721 is an equidigital number, since it uses as much as digits as its factorization.

2721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 910.

The product of its digits is 28, while the sum is 12.

The square root of 2721 is about 52.1632054230. The cubic root of 2721 is about 13.9607745538.

Adding to 2721 its reverse (1272), we get a palindrome (3993).

The spelling of 2721 in words is "two thousand, seven hundred twenty-one", and thus it is an iban number.