21456566 has 4 divisors (see below), whose sum is σ = 32184852. Its totient is φ = 10728282.

The previous prime is 21456563. The next prime is 21456577. The reversal of 21456566 is 66565412.

It is a semiprime because it is the product of two primes.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5364140 + ... + 5364143.

It is an arithmetic number, because the mean of its divisors is an integer number (8046213).

Almost surely, 2^21456566 is an apocalyptic number.

21456566 is a deficient number, since it is larger than the sum of its proper divisors (10728286).

21456566 is a wasteful number, since it uses less digits than its factorization.

21456566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10728285.

The product of its digits is 43200, while the sum is 35.

The square root of 21456566 is about 4632.1232712440. The cubic root of 21456566 is about 277.8775144902.

It can be divided in two parts, 21456 and 566, that added together give a palindrome (22022).

The spelling of 21456566 in words is "twenty-one million, four hundred fifty-six thousand, five hundred sixty-six".