21867811 has 4 divisors (see below), whose sum is σ = 24991792. Its totient is φ = 18743832.

The previous prime is 21867773. The next prime is 21867821. The reversal of 21867811 is 11876812.

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 21867811 - 2⁷ = 21867683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21867821) 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 3 ways as a sum of consecutive naturals, for example, 1561980 + ... + 1561993.

It is an arithmetic number, because the mean of its divisors is an integer number (6247948).

Almost surely, 2^21867811 is an apocalyptic number.

21867811 is a deficient number, since it is larger than the sum of its proper divisors (3123981).

21867811 is an equidigital number, since it uses as much as digits as its factorization.

21867811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3123980.

The product of its digits is 5376, while the sum is 34.

The square root of 21867811 is about 4676.3031338869. The cubic root of 21867811 is about 279.6415950024.

Subtracting from 21867811 its reverse (11876812), we obtain a palindrome (9990999).

The spelling of 21867811 in words is "twenty-one million, eight hundred sixty-seven thousand, eight hundred eleven".