21105187 has 2 divisors, whose sum is σ = 21105188. Its totient is φ = 21105186.

The previous prime is 21105179. The next prime is 21105197. The reversal of 21105187 is 78150112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21105187 - 2³ = 21105179 is a prime.

It is not a weakly prime, because it can be changed into another prime (21105107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552593 + 10552594.

It is an arithmetic number, because the mean of its divisors is an integer number (10552594).

Almost surely, 2^21105187 is an apocalyptic number.

21105187 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105187 is an equidigital number, since it uses as much as digits as its factorization.

21105187 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 560, while the sum is 25.

The square root of 21105187 is about 4594.0382018438. The cubic root of 21105187 is about 276.3522902860.

Adding to 21105187 its reverse (78150112), we get a palindrome (99255299).

The spelling of 21105187 in words is "twenty-one million, one hundred five thousand, one hundred eighty-seven".