21066109 has 2 divisors, whose sum is σ = 21066110. Its totient is φ = 21066108.

The previous prime is 21066107. The next prime is 21066113. The reversal of 21066109 is 90166012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20702500 + 363609 = 4550^2 + 603^2 .

It is a cyclic number.

It is not a de Polignac number, because 21066109 - 2¹ = 21066107 is a prime.

Together with 21066107, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21066107) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10533054 + 10533055.

It is an arithmetic number, because the mean of its divisors is an integer number (10533055).

Almost surely, 2^21066109 is an apocalyptic number.

It is an amenable number.

21066109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21066109 is an equidigital number, since it uses as much as digits as its factorization.

21066109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 21066109 is about 4589.7831103441. The cubic root of 21066109 is about 276.1816218633.

The spelling of 21066109 in words is "twenty-one million, sixty-six thousand, one hundred nine".