21644099 has 2 divisors, whose sum is σ = 21644100. Its totient is φ = 21644098.

The previous prime is 21644089. The next prime is 21644101. The reversal of 21644099 is 99044612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21644099 - 2¹⁶ = 21578563 is a prime.

It is a Sophie Germain prime.

Together with 21644101, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21644039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822049 + 10822050.

It is an arithmetic number, because the mean of its divisors is an integer number (10822050).

Almost surely, 2^21644099 is an apocalyptic number.

21644099 is a deficient number, since it is larger than the sum of its proper divisors (1).

21644099 is an equidigital number, since it uses as much as digits as its factorization.

21644099 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21644099 is about 4652.3218934205. The cubic root of 21644099 is about 278.6847284282.

The spelling of 21644099 in words is "twenty-one million, six hundred forty-four thousand, ninety-nine".