2105721 has 6 divisors (see below), whose sum is σ = 3041610. Its totient is φ = 1403808.

The previous prime is 2105717. The next prime is 2105729. The reversal of 2105721 is 1275012.

It can be written as a sum of positive squares in only one way, i.e., 1929321 + 176400 = 1389^2 + 420^2 .

It is not a de Polignac number, because 2105721 - 2² = 2105717 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2105694 and 2105703.

It is not an unprimeable number, because it can be changed into a prime (2105729) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 116976 + ... + 116993.

It is an arithmetic number, because the mean of its divisors is an integer number (506935).

2^2105721 is an apocalyptic number.

It is an amenable number.

2105721 is a deficient number, since it is larger than the sum of its proper divisors (935889).

2105721 is a wasteful number, since it uses less digits than its factorization.

2105721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233975 (or 233972 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 2105721 is about 1451.1102645905. The cubic root of 2105721 is about 128.1740998412.

The spelling of 2105721 in words is "two million, one hundred five thousand, seven hundred twenty-one".