21219911 has 4 divisors (see below), whose sum is σ = 21229392. Its totient is φ = 21210432.

The previous prime is 21219901. The next prime is 21219917. The reversal of 21219911 is 11991212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21219911 - 2¹⁰ = 21218887 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 (21219917) 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, 695 + ... + 6551.

It is an arithmetic number, because the mean of its divisors is an integer number (5307348).

Almost surely, 2^21219911 is an apocalyptic number.

21219911 is a deficient number, since it is larger than the sum of its proper divisors (9481).

21219911 is an equidigital number, since it uses as much as digits as its factorization.

21219911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9480.

The product of its digits is 324, while the sum is 26.

The square root of 21219911 is about 4606.5074622755. The cubic root of 21219911 is about 276.8521194958.

The spelling of 21219911 in words is "twenty-one million, two hundred nineteen thousand, nine hundred eleven".