20321261 has 2 divisors, whose sum is σ = 20321262. Its totient is φ = 20321260.

The previous prime is 20321243. The next prime is 20321263. The reversal of 20321261 is 16212302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13920361 + 6400900 = 3731^2 + 2530^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20321261 is a prime.

Together with 20321263, 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 (20321263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10160630 + 10160631.

It is an arithmetic number, because the mean of its divisors is an integer number (10160631).

Almost surely, 2^20321261 is an apocalyptic number.

It is an amenable number.

20321261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20321261 is an equidigital number, since it uses as much as digits as its factorization.

20321261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 20321261 is about 4507.9109352337. The cubic root of 20321261 is about 272.8874425855.

Adding to 20321261 its reverse (16212302), we get a palindrome (36533563).

The spelling of 20321261 in words is "twenty million, three hundred twenty-one thousand, two hundred sixty-one".