20261 has 2 divisors, whose sum is σ = 20262. Its totient is φ = 20260.

The previous prime is 20249. The next prime is 20269. The reversal of 20261 is 16202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11236 + 9025 = 106^2 + 95^2 .

It is a cyclic number.

It is not a de Polignac number, because 20261 - 2¹⁰ = 19237 is a prime.

It is a Chen prime.

It is a magnanimous number.

It is a plaindrome in base 6.

It is a nialpdrome in base 12 and base 14.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10130 + 10131.

It is an arithmetic number, because the mean of its divisors is an integer number (10131).

2²⁰²⁶¹ is an apocalyptic number.

It is an amenable number.

20261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20261 is an equidigital number, since it uses as much as digits as its factorization.

20261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 20261 is about 142.3411395205. The cubic root of 20261 is about 27.2617433884.

Adding to 20261 its reverse (16202), we get a palindrome (36463).

The spelling of 20261 in words is "twenty thousand, two hundred sixty-one".