21080261 has 2 divisors, whose sum is σ = 21080262. Its totient is φ = 21080260.

The previous prime is 21080249. The next prime is 21080317. The reversal of 21080261 is 16208012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13184161 + 7896100 = 3631^2 + 2810^2 .

It is a cyclic number.

It is not a de Polignac number, because 21080261 - 2¹⁰ = 21079237 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21080201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10540130 + 10540131.

It is an arithmetic number, because the mean of its divisors is an integer number (10540131).

Almost surely, 2^21080261 is an apocalyptic number.

It is an amenable number.

21080261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21080261 is an equidigital number, since it uses as much as digits as its factorization.

21080261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21080261 is about 4591.3245365581. The cubic root of 21080261 is about 276.2434533641.

Adding to 21080261 its reverse (16208012), we get a palindrome (37288273).

The spelling of 21080261 in words is "twenty-one million, eighty thousand, two hundred sixty-one".