21066321 has 16 divisors (see below), whose sum is σ = 29589120. Its totient is φ = 13305600.

The previous prime is 21066319. The next prime is 21066323. The reversal of 21066321 is 12366012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21066319) and next prime (21066323).

It is not a de Polignac number, because 21066321 - 2¹ = 21066319 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21066323) 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, 6121 + ... + 8921.

It is an arithmetic number, because the mean of its divisors is an integer number (1849320).

Almost surely, 2^21066321 is an apocalyptic number.

It is an amenable number.

21066321 is a deficient number, since it is larger than the sum of its proper divisors (8522799).

21066321 is a wasteful number, since it uses less digits than its factorization.

21066321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2936.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21066321 is about 4589.8062050592. The cubic root of 21066321 is about 276.1825483168.

The spelling of 21066321 in words is "twenty-one million, sixty-six thousand, three hundred twenty-one".