21066609 has 16 divisors (see below), whose sum is σ = 28727552. Its totient is φ = 13728528.

The previous prime is 21066607. The next prime is 21066613. The reversal of 21066609 is 90666012.

It is not a de Polignac number, because 21066609 - 2¹ = 21066607 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21066601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32442 + ... + 33084.

It is an arithmetic number, because the mean of its divisors is an integer number (1795472).

Almost surely, 2^21066609 is an apocalyptic number.

It is an amenable number.

21066609 is a deficient number, since it is larger than the sum of its proper divisors (7660943).

21066609 is a wasteful number, since it uses less digits than its factorization.

21066609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 876.

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 21066609 is about 4589.8375788256. The cubic root of 21066609 is about 276.1838068851.

The spelling of 21066609 in words is "twenty-one million, sixty-six thousand, six hundred nine".