21998111 has 2 divisors, whose sum is σ = 21998112. Its totient is φ = 21998110.

The previous prime is 21998107. The next prime is 21998113. The reversal of 21998111 is 11189912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21998111 - 2² = 21998107 is a prime.

Together with 21998113, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21998113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10999055 + 10999056.

It is an arithmetic number, because the mean of its divisors is an integer number (10999056).

Almost surely, 2^21998111 is an apocalyptic number.

21998111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21998111 is an equidigital number, since it uses as much as digits as its factorization.

21998111 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 32.

The square root of 21998111 is about 4690.2143874241. The cubic root of 21998111 is about 280.1959130598.

The spelling of 21998111 in words is "twenty-one million, nine hundred ninety-eight thousand, one hundred eleven".