21604166 has 8 divisors (see below), whose sum is σ = 32542560. Its totient is φ = 10756648.

The previous prime is 21604151. The next prime is 21604169. The reversal of 21604166 is 66140612.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604169) 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, 22121 + ... + 23076.

It is an arithmetic number, because the mean of its divisors is an integer number (4067820).

Almost surely, 2^21604166 is an apocalyptic number.

21604166 is a deficient number, since it is larger than the sum of its proper divisors (10938394).

21604166 is a wasteful number, since it uses less digits than its factorization.

21604166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45438.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 21604166 is about 4648.0281840798. The cubic root of 21604166 is about 278.5132333650.

Adding to 21604166 its reverse (66140612), we get a palindrome (87744778).

The spelling of 21604166 in words is "twenty-one million, six hundred four thousand, one hundred sixty-six".