21108586 has 4 divisors (see below), whose sum is σ = 31662882. Its totient is φ = 10554292.

The previous prime is 21108557. The next prime is 21108587. The reversal of 21108586 is 68580112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20839225 + 269361 = 4565^2 + 519^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21108587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5277145 + ... + 5277148.

Almost surely, 2^21108586 is an apocalyptic number.

21108586 is a deficient number, since it is larger than the sum of its proper divisors (10554296).

21108586 is a wasteful number, since it uses less digits than its factorization.

21108586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10554295.

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 21108586 is about 4594.4081229251. The cubic root of 21108586 is about 276.3671250438.

Adding to 21108586 its reverse (68580112), we get a palindrome (89688698).

The spelling of 21108586 in words is "twenty-one million, one hundred eight thousand, five hundred eighty-six".