20887891 has 2 divisors, whose sum is σ = 20887892. Its totient is φ = 20887890.

The previous prime is 20887879. The next prime is 20887903. The reversal of 20887891 is 19878802.

It is a balanced prime because it is at equal distance from previous prime (20887879) and next prime (20887903).

It is a cyclic number.

It is not a de Polignac number, because 20887891 - 2¹⁵ = 20855123 is a prime.

It is not a weakly prime, because it can be changed into another prime (20887861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10443945 + 10443946.

It is an arithmetic number, because the mean of its divisors is an integer number (10443946).

Almost surely, 2^20887891 is an apocalyptic number.

20887891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20887891 is an equidigital number, since it uses as much as digits as its factorization.

20887891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64512, while the sum is 43.

The square root of 20887891 is about 4570.3272311728. The cubic root of 20887891 is about 275.4005886366.

It can be divided in two parts, 20 and 887891, that multiplied together give a triangular number (17757820 = T₅₉₅₉).

The spelling of 20887891 in words is "twenty million, eight hundred eighty-seven thousand, eight hundred ninety-one".