21365566 has 8 divisors (see below), whose sum is σ = 33933600. Its totient is φ = 10054368.

The previous prime is 21365543. The next prime is 21365569. The reversal of 21365566 is 66556312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Harshad number since it is a multiple of its sum of digits (34), and also a Moran number because the ratio is a prime number: 628399 = 21365566 / (2 + 1 + 3 + 6 + 5 + 5 + 6 + 6).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 314166 + ... + 314233.

It is an arithmetic number, because the mean of its divisors is an integer number (4241700).

Almost surely, 2^21365566 is an apocalyptic number.

21365566 is a deficient number, since it is larger than the sum of its proper divisors (12568034).

21365566 is a wasteful number, since it uses less digits than its factorization.

21365566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 628418.

The product of its digits is 32400, while the sum is 34.

The square root of 21365566 is about 4622.2901250354. The cubic root of 21365566 is about 277.4841199689.

The spelling of 21365566 in words is "twenty-one million, three hundred sixty-five thousand, five hundred sixty-six".