2167721 has 8 divisors (see below), whose sum is σ = 2374920. Its totient is φ = 1969408.

The previous prime is 2167717. The next prime is 2167723. The reversal of 2167721 is 1277612.

It can be written as a sum of positive squares in 4 ways, for example, as 577600 + 1590121 = 760^2 + 1261^2 .

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 2167721 - 2² = 2167717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2167723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1706 + ... + 2691.

It is an arithmetic number, because the mean of its divisors is an integer number (296865).

2^2167721 is an apocalyptic number.

It is an amenable number.

2167721 is a deficient number, since it is larger than the sum of its proper divisors (207199).

2167721 is a wasteful number, since it uses less digits than its factorization.

2167721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4443.

The product of its digits is 1176, while the sum is 26.

The square root of 2167721 is about 1472.3182400555. The cubic root of 2167721 is about 129.4199203781.

It can be divided in two parts, 21 and 67721, that multiplied together give a triangular number (1422141 = T₁₆₈₆).

The spelling of 2167721 in words is "two million, one hundred sixty-seven thousand, seven hundred twenty-one".