21318811 has 4 divisors (see below), whose sum is σ = 21838824. Its totient is φ = 20798800.

The previous prime is 21318767. The next prime is 21318821. The reversal of 21318811 is 11881312.

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 21318811 - 2⁹ = 21318299 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21318821) 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, 259945 + ... + 260026.

It is an arithmetic number, because the mean of its divisors is an integer number (5459706).

Almost surely, 2^21318811 is an apocalyptic number.

21318811 is a deficient number, since it is larger than the sum of its proper divisors (520013).

21318811 is an equidigital number, since it uses as much as digits as its factorization.

21318811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520012.

The product of its digits is 384, while the sum is 25.

The square root of 21318811 is about 4617.2297971836. The cubic root of 21318811 is about 277.2815628075.

The spelling of 21318811 in words is "twenty-one million, three hundred eighteen thousand, eight hundred eleven".