21043786 has 4 divisors (see below), whose sum is σ = 31565682. Its totient is φ = 10521892.

The previous prime is 21043753. The next prime is 21043793. The reversal of 21043786 is 68734012.

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., 11771761 + 9272025 = 3431^2 + 3045^2 .

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 an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5260945 + ... + 5260948.

Almost surely, 2^21043786 is an apocalyptic number.

21043786 is a deficient number, since it is larger than the sum of its proper divisors (10521896).

21043786 is a wasteful number, since it uses less digits than its factorization.

21043786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10521895.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 21043786 is about 4587.3506515199. The cubic root of 21043786 is about 276.0840341328.

Adding to 21043786 its reverse (68734012), we get a palindrome (89777798).

The spelling of 21043786 in words is "twenty-one million, forty-three thousand, seven hundred eighty-six".