21043963 has 16 divisors (see below), whose sum is σ = 22935040. Its totient is φ = 19245600.

The previous prime is 21043949. The next prime is 21043973. The reversal of 21043963 is 36934012.

It is a cyclic number.

It is not a de Polignac number, because 21043963 - 2¹³ = 21035771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21043973) 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 in 15 ways as a sum of consecutive naturals, for example, 77518 + ... + 77788.

It is an arithmetic number, because the mean of its divisors is an integer number (1433440).

Almost surely, 2^21043963 is an apocalyptic number.

21043963 is a deficient number, since it is larger than the sum of its proper divisors (1891077).

21043963 is a wasteful number, since it uses less digits than its factorization.

21043963 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418.

The product of its (nonzero) digits is 3888, while the sum is 28.

The square root of 21043963 is about 4587.3699436605. The cubic root of 21043963 is about 276.0848081813.

Adding to 21043963 its reverse (36934012), we get a palindrome (57977975).

The spelling of 21043963 in words is "twenty-one million, forty-three thousand, nine hundred sixty-three".