21043966 has 16 divisors (see below), whose sum is σ = 32876640. Its totient is φ = 10090080.

The previous prime is 21043949. The next prime is 21043973. The reversal of 21043966 is 66934012.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 7951 + ... + 10261.

It is an arithmetic number, because the mean of its divisors is an integer number (2054790).

Almost surely, 2^21043966 is an apocalyptic number.

21043966 is a deficient number, since it is larger than the sum of its proper divisors (11832674).

21043966 is a wasteful number, since it uses less digits than its factorization.

21043966 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2499.

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 21043966 is about 4587.3702706453. The cubic root of 21043966 is about 276.0848213007.

Adding to 21043966 its reverse (66934012), we get a palindrome (87977978).

The spelling of 21043966 in words is "twenty-one million, forty-three thousand, nine hundred sixty-six".