21811109 has 2 divisors, whose sum is σ = 21811110. Its totient is φ = 21811108.

The previous prime is 21811087. The next prime is 21811117. The reversal of 21811109 is 90111812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21808900 + 2209 = 4670^2 + 47^2 .

It is a cyclic number.

It is not a de Polignac number, because 21811109 - 2²⁴ = 5033893 is a prime.

It is a super-3 number, since 3×21811109³ (a number of 23 digits) contains 333 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21811409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10905554 + 10905555.

It is an arithmetic number, because the mean of its divisors is an integer number (10905555).

Almost surely, 2^21811109 is an apocalyptic number.

It is an amenable number.

21811109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21811109 is an equidigital number, since it uses as much as digits as its factorization.

21811109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 21811109 is about 4670.2365036473. The cubic root of 21811109 is about 279.3996875054.

The spelling of 21811109 in words is "twenty-one million, eight hundred eleven thousand, one hundred nine".