2521721 has 2 divisors, whose sum is σ = 2521722. Its totient is φ = 2521720.

The previous prime is 2521711. The next prime is 2521723. The reversal of 2521721 is 1271252.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2446096 + 75625 = 1564^2 + 275^2 .

It is a cyclic number.

It is not a de Polignac number, because 2521721 - 2¹⁰ = 2520697 is a prime.

It is a Sophie Germain prime.

Together with 2521723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 2521693 and 2521702.

It is not a weakly prime, because it can be changed into another prime (2521723) 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 as a sum of consecutive naturals, namely, 1260860 + 1260861.

It is an arithmetic number, because the mean of its divisors is an integer number (1260861).

2^2521721 is an apocalyptic number.

It is an amenable number.

2521721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2521721 is an equidigital number, since it uses as much as digits as its factorization.

2521721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 280, while the sum is 20.

The square root of 2521721 is about 1587.9927581699. The cubic root of 2521721 is about 136.1128136890.

Adding to 2521721 its reverse (1271252), we get a palindrome (3792973).

The spelling of 2521721 in words is "two million, five hundred twenty-one thousand, seven hundred twenty-one".