21042566 has 32 divisors (see below), whose sum is σ = 35212320. Its totient is φ = 9386496.

The previous prime is 21042563. The next prime is 21042577. The reversal of 21042566 is 66524012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042563) 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, 53900 + ... + 54288.

It is an arithmetic number, because the mean of its divisors is an integer number (1100385).

Almost surely, 2^21042566 is an apocalyptic number.

21042566 is a deficient number, since it is larger than the sum of its proper divisors (14169754).

21042566 is a wasteful number, since it uses less digits than its factorization.

21042566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 488.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21042566 is about 4587.2176752363. The cubic root of 21042566 is about 276.0786987647.

Adding to 21042566 its reverse (66524012), we get a palindrome (87566578).

The spelling of 21042566 in words is "twenty-one million, forty-two thousand, five hundred sixty-six".