21089851 has 2 divisors, whose sum is σ = 21089852. Its totient is φ = 21089850.

The previous prime is 21089839. The next prime is 21089857. The reversal of 21089851 is 15898012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21089851 - 2⁵ = 21089819 is a prime.

It is not a weakly prime, because it can be changed into another prime (21089857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10544925 + 10544926.

It is an arithmetic number, because the mean of its divisors is an integer number (10544926).

Almost surely, 2^21089851 is an apocalyptic number.

21089851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21089851 is an equidigital number, since it uses as much as digits as its factorization.

21089851 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 21089851 is about 4592.3687787459. The cubic root of 21089851 is about 276.2853373030.

The spelling of 21089851 in words is "twenty-one million, eighty-nine thousand, eight hundred fifty-one".