20018891 has 2 divisors, whose sum is σ = 20018892. Its totient is φ = 20018890.

The previous prime is 20018881. The next prime is 20018893. The reversal of 20018891 is 19881002.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20018891 is a prime.

Together with 20018893, 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 (20018893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10009445 + 10009446.

It is an arithmetic number, because the mean of its divisors is an integer number (10009446).

Almost surely, 2^20018891 is an apocalyptic number.

20018891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20018891 is an equidigital number, since it uses as much as digits as its factorization.

20018891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 20018891 is about 4474.2475345023. The cubic root of 20018891 is about 271.5271982041.

Adding to 20018891 its reverse (19881002), we get a palindrome (39899893).

It can be divided in two parts, 200 and 18891, that added together give a palindrome (19091).

The spelling of 20018891 in words is "twenty million, eighteen thousand, eight hundred ninety-one".