20023561 has 2 divisors, whose sum is σ = 20023562. Its totient is φ = 20023560.

The previous prime is 20023537. The next prime is 20023567. The reversal of 20023561 is 16532002.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17065161 + 2958400 = 4131^2 + 1720^2 .

It is a cyclic number.

It is not a de Polignac number, because 20023561 - 2⁹ = 20023049 is a prime.

It is not a weakly prime, because it can be changed into another prime (20023567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10011780 + 10011781.

It is an arithmetic number, because the mean of its divisors is an integer number (10011781).

Almost surely, 2^20023561 is an apocalyptic number.

It is an amenable number.

20023561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20023561 is an equidigital number, since it uses as much as digits as its factorization.

20023561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 20023561 is about 4474.7693795323. The cubic root of 20023561 is about 271.5483104863.

Adding to 20023561 its reverse (16532002), we get a palindrome (36555563).

The spelling of 20023561 in words is "twenty million, twenty-three thousand, five hundred sixty-one".