21904066 has 8 divisors (see below), whose sum is σ = 32960700. Its totient is φ = 10917168.

The previous prime is 21904061. The next prime is 21904081. The reversal of 21904066 is 66040912.

It can be written as a sum of positive squares in 2 ways, for example, as 21893041 + 11025 = 4679^2 + 105^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21904061) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16641 + ... + 17908.

Almost surely, 2^21904066 is an apocalyptic number.

21904066 is a deficient number, since it is larger than the sum of its proper divisors (11056634).

21904066 is a wasteful number, since it uses less digits than its factorization.

21904066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34868.

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21904066 is about 4680.1779880684. The cubic root of 21904066 is about 279.7960504606.

Adding to 21904066 its reverse (66040912), we get a palindrome (87944978).

The spelling of 21904066 in words is "twenty-one million, nine hundred four thousand, sixty-six".