20563891 has 2 divisors, whose sum is σ = 20563892. Its totient is φ = 20563890.

The previous prime is 20563889. The next prime is 20563913. The reversal of 20563891 is 19836502.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20563891 - 2¹ = 20563889 is a prime.

It is a super-2 number, since 2×20563891² = 845747226119762, which contains 22 as substring.

Together with 20563889, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20563811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10281945 + 10281946.

It is an arithmetic number, because the mean of its divisors is an integer number (10281946).

Almost surely, 2^20563891 is an apocalyptic number.

20563891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20563891 is an equidigital number, since it uses as much as digits as its factorization.

20563891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 20563891 is about 4534.7426608353. The cubic root of 20563891 is about 273.9692144004.

The spelling of 20563891 in words is "twenty million, five hundred sixty-three thousand, eight hundred ninety-one".