2159721 has 12 divisors (see below), whose sum is σ = 3133572. Its totient is φ = 1433376.

The previous prime is 2159719. The next prime is 2159767. The reversal of 2159721 is 1279512.

It can be written as a sum of positive squares in 2 ways, for example, as 632025 + 1527696 = 795^2 + 1236^2 .

It is not a de Polignac number, because 2159721 - 2¹ = 2159719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2159701) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2475 + ... + 3231.

It is an arithmetic number, because the mean of its divisors is an integer number (261131).

2^2159721 is an apocalyptic number.

It is an amenable number.

2159721 is a deficient number, since it is larger than the sum of its proper divisors (973851).

2159721 is a wasteful number, since it uses less digits than its factorization.

2159721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1080 (or 1077 counting only the distinct ones).

The product of its digits is 1260, while the sum is 27.

The square root of 2159721 is about 1469.5989248771. The cubic root of 2159721 is about 129.2605155393.

The spelling of 2159721 in words is "two million, one hundred fifty-nine thousand, seven hundred twenty-one".