21404566 has 4 divisors (see below), whose sum is σ = 32106852. Its totient is φ = 10702282.

The previous prime is 21404563. The next prime is 21404567. The reversal of 21404566 is 66540412.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5351140 + ... + 5351143.

It is an arithmetic number, because the mean of its divisors is an integer number (8026713).

Almost surely, 2^21404566 is an apocalyptic number.

21404566 is a deficient number, since it is larger than the sum of its proper divisors (10702286).

21404566 is a wasteful number, since it uses less digits than its factorization.

21404566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10702285.

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 21404566 is about 4626.5068896523. The cubic root of 21404566 is about 277.6528541323.

Adding to 21404566 its reverse (66540412), we get a palindrome (87944978).

The spelling of 21404566 in words is "twenty-one million, four hundred four thousand, five hundred sixty-six".