2561021 has 2 divisors, whose sum is σ = 2561022. Its totient is φ = 2561020.

The previous prime is 2561017. The next prime is 2561023. The reversal of 2561021 is 1201652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2524921 + 36100 = 1589^2 + 190^2 .

It is a cyclic number.

It is not a de Polignac number, because 2561021 - 2² = 2561017 is a prime.

Together with 2561023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2561023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1280510 + 1280511.

It is an arithmetic number, because the mean of its divisors is an integer number (1280511).

2^2561021 is an apocalyptic number.

It is an amenable number.

2561021 is a deficient number, since it is larger than the sum of its proper divisors (1).

2561021 is an equidigital number, since it uses as much as digits as its factorization.

2561021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 2561021 is about 1600.3190306936. The cubic root of 2561021 is about 136.8162596236.

Adding to 2561021 its reverse (1201652), we get a palindrome (3762673).

The spelling of 2561021 in words is "two million, five hundred sixty-one thousand, twenty-one".