21066309 has 12 divisors (see below), whose sum is σ = 33195552. Its totient is φ = 12767400.

The previous prime is 21066299. The next prime is 21066319. The reversal of 21066309 is 90366012.

It is a happy number.

21066309 is a `hidden beast` number, since 21 + 0 + 6 + 630 + 9 = 666.

It is an interprime number because it is at equal distance from previous prime (21066299) and next prime (21066319).

It is not a de Polignac number, because 21066309 - 2⁷ = 21066181 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21066319) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 106297 + ... + 106494.

It is an arithmetic number, because the mean of its divisors is an integer number (2766296).

Almost surely, 2^21066309 is an apocalyptic number.

It is an amenable number.

21066309 is a deficient number, since it is larger than the sum of its proper divisors (12129243).

21066309 is a wasteful number, since it uses less digits than its factorization.

21066309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212808 (or 212805 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 27.

The square root of 21066309 is about 4589.8048978143. The cubic root of 21066309 is about 276.1824958762.

The spelling of 21066309 in words is "twenty-one million, sixty-six thousand, three hundred nine".