21879911 has 4 divisors (see below), whose sum is σ = 21890352. Its totient is φ = 21869472.

The previous prime is 21879899. The next prime is 21879917. The reversal of 21879911 is 11997812.

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 21879911 - 2¹⁰ = 21878887 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 (21879917) 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, 866 + ... + 6671.

It is an arithmetic number, because the mean of its divisors is an integer number (5472588).

Almost surely, 2^21879911 is an apocalyptic number.

21879911 is a deficient number, since it is larger than the sum of its proper divisors (10441).

21879911 is an equidigital number, since it uses as much as digits as its factorization.

21879911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10440.

The product of its digits is 9072, while the sum is 38.

The square root of 21879911 is about 4677.5967119879. The cubic root of 21879911 is about 279.6931630263.

The spelling of 21879911 in words is "twenty-one million, eight hundred seventy-nine thousand, nine hundred eleven".