20012561 has 2 divisors, whose sum is σ = 20012562. Its totient is φ = 20012560.

The previous prime is 20012543. The next prime is 20012563. The reversal of 20012561 is 16521002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16248961 + 3763600 = 4031^2 + 1940^2 .

It is a cyclic number.

It is not a de Polignac number, because 20012561 - 2¹⁸ = 19750417 is a prime.

Together with 20012563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20012563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10006280 + 10006281.

It is an arithmetic number, because the mean of its divisors is an integer number (10006281).

Almost surely, 2^20012561 is an apocalyptic number.

It is an amenable number.

20012561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20012561 is an equidigital number, since it uses as much as digits as its factorization.

20012561 is an odious number, because the sum of its binary digits is odd.

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

The square root of 20012561 is about 4473.5400970596. The cubic root of 20012561 is about 271.4985760999.

Adding to 20012561 its reverse (16521002), we get a palindrome (36533563).

The spelling of 20012561 in words is "twenty million, twelve thousand, five hundred sixty-one".