21021943 has 4 divisors (see below), whose sum is σ = 21173320. Its totient is φ = 20870568.

The previous prime is 21021899. The next prime is 21021953. The reversal of 21021943 is 34912012.

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

It is a cyclic number.

It is not a de Polignac number, because 21021943 - 2⁹ = 21021431 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021953) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 75480 + ... + 75757.

It is an arithmetic number, because the mean of its divisors is an integer number (5293330).

Almost surely, 2^21021943 is an apocalyptic number.

21021943 is a deficient number, since it is larger than the sum of its proper divisors (151377).

21021943 is a wasteful number, since it uses less digits than its factorization.

21021943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151376.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21021943 is about 4584.9692474432. The cubic root of 21021943 is about 275.9884779549.

Adding to 21021943 its reverse (34912012), we get a palindrome (55933955).

The spelling of 21021943 in words is "twenty-one million, twenty-one thousand, nine hundred forty-three".