2101721 has 2 divisors, whose sum is σ = 2101722. Its totient is φ = 2101720.

The previous prime is 2101703. The next prime is 2101733. The reversal of 2101721 is 1271012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1123600 + 978121 = 1060^2 + 989^2 .

It is a cyclic number.

It is not a de Polignac number, because 2101721 - 2⁶ = 2101657 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2101696 and 2101705.

It is not a weakly prime, because it can be changed into another prime (2101741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1050860 + 1050861.

It is an arithmetic number, because the mean of its divisors is an integer number (1050861).

2^2101721 is an apocalyptic number.

It is an amenable number.

2101721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2101721 is an equidigital number, since it uses as much as digits as its factorization.

2101721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28, while the sum is 14.

The square root of 2101721 is about 1449.7313544240. The cubic root of 2101721 is about 128.0928891174.

Adding to 2101721 its reverse (1271012), we get a palindrome (3372733).

The spelling of 2101721 in words is "two million, one hundred one thousand, seven hundred twenty-one".