21164943 has 4 divisors (see below), whose sum is σ = 28219928. Its totient is φ = 14109960.

The previous prime is 21164939. The next prime is 21164953. The reversal of 21164943 is 34946112.

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

It is not a de Polignac number, because 21164943 - 2² = 21164939 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21164943.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164953) 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, 3527488 + ... + 3527493.

It is an arithmetic number, because the mean of its divisors is an integer number (7054982).

Almost surely, 2^21164943 is an apocalyptic number.

21164943 is a deficient number, since it is larger than the sum of its proper divisors (7054985).

21164943 is an equidigital number, since it uses as much as digits as its factorization.

21164943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7054984.

The product of its digits is 5184, while the sum is 30.

The square root of 21164943 is about 4600.5372512349. The cubic root of 21164943 is about 276.6128604579.

The spelling of 21164943 in words is "twenty-one million, one hundred sixty-four thousand, nine hundred forty-three".