20561903 has 2 divisors, whose sum is σ = 20561904. Its totient is φ = 20561902.

The previous prime is 20561867. The next prime is 20561911. The reversal of 20561903 is 30916502.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20561903 - 2⁸ = 20561647 is a prime.

It is a super-3 number, since 3×20561903³ (a number of 23 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20561923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10280951 + 10280952.

It is an arithmetic number, because the mean of its divisors is an integer number (10280952).

Almost surely, 2^20561903 is an apocalyptic number.

20561903 is a deficient number, since it is larger than the sum of its proper divisors (1).

20561903 is an equidigital number, since it uses as much as digits as its factorization.

20561903 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 20561903 is about 4534.5234589756. The cubic root of 20561903 is about 273.9603855209.

The spelling of 20561903 in words is "twenty million, five hundred sixty-one thousand, nine hundred three".