2721661 has 4 divisors (see below), whose sum is σ = 2725792. Its totient is φ = 2717532.

The previous prime is 2721619. The next prime is 2721671. The reversal of 2721661 is 1661272.

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 a cyclic number.

It is not a de Polignac number, because 2721661 - 2⁷ = 2721533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2721671) 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, 831 + ... + 2476.

It is an arithmetic number, because the mean of its divisors is an integer number (681448).

2^2721661 is an apocalyptic number.

It is an amenable number.

2721661 is a deficient number, since it is larger than the sum of its proper divisors (4131).

2721661 is an equidigital number, since it uses as much as digits as its factorization.

2721661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4130.

The product of its digits is 1008, while the sum is 25.

The square root of 2721661 is about 1649.7457379851. The cubic root of 2721661 is about 139.6190493787.

The spelling of 2721661 in words is "two million, seven hundred twenty-one thousand, six hundred sixty-one".