21116811 has 4 divisors (see below), whose sum is σ = 28155752. Its totient is φ = 14077872.

The previous prime is 21116801. The next prime is 21116819. The reversal of 21116811 is 11861112.

It is a happy number.

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

It is not a de Polignac number, because 21116811 - 2⁹ = 21116299 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21116819) 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, 3519466 + ... + 3519471.

It is an arithmetic number, because the mean of its divisors is an integer number (7038938).

Almost surely, 2^21116811 is an apocalyptic number.

21116811 is a deficient number, since it is larger than the sum of its proper divisors (7038941).

21116811 is an equidigital number, since it uses as much as digits as its factorization.

21116811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7038940.

The product of its digits is 96, while the sum is 21.

The square root of 21116811 is about 4595.3031456042. The cubic root of 21116811 is about 276.4030160382.

Adding to 21116811 its reverse (11861112), we get a palindrome (32977923).

The spelling of 21116811 in words is "twenty-one million, one hundred sixteen thousand, eight hundred eleven".