21899811 has 4 divisors (see below), whose sum is σ = 29199752. Its totient is φ = 14599872.

The previous prime is 21899803. The next prime is 21899831. The reversal of 21899811 is 11899812.

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

It is not a de Polignac number, because 21899811 - 2³ = 21899803 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 21899811.

It is not an unprimeable number, because it can be changed into a prime (21899831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3649966 + ... + 3649971.

It is an arithmetic number, because the mean of its divisors is an integer number (7299938).

Almost surely, 2^21899811 is an apocalyptic number.

21899811 is a deficient number, since it is larger than the sum of its proper divisors (7299941).

21899811 is an equidigital number, since it uses as much as digits as its factorization.

21899811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7299940.

The product of its digits is 10368, while the sum is 39.

The square root of 21899811 is about 4679.7233892614. The cubic root of 21899811 is about 279.7779319175. Note that the first 3 decimals are identical.

Subtracting from 21899811 its reverse (11899812), we obtain a palindrome (9999999).

The spelling of 21899811 in words is "twenty-one million, eight hundred ninety-nine thousand, eight hundred eleven".