21481566 has 8 divisors (see below), whose sum is σ = 42963144. Its totient is φ = 7160520.

The previous prime is 21481561. The next prime is 21481567. The reversal of 21481566 is 66518412.

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

21481566 is an admirable number.

It is a super-2 number, since 2×21481566² = 922915355624712, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481561) 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 in 3 ways as a sum of consecutive naturals, for example, 1790125 + ... + 1790136.

It is an arithmetic number, because the mean of its divisors is an integer number (5370393).

Almost surely, 2^21481566 is an apocalyptic number.

21481566 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21481566 is a wasteful number, since it uses less digits than its factorization.

21481566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3580266.

The product of its digits is 11520, while the sum is 33.

The square root of 21481566 is about 4634.8210321435. The cubic root of 21481566 is about 277.9853950887.

Adding to 21481566 its reverse (66518412), we get a palindrome (87999978).

The spelling of 21481566 in words is "twenty-one million, four hundred eighty-one thousand, five hundred sixty-six".