21418164 has 72 divisors (see below), whose sum is σ = 58181760. Its totient is φ = 6619392.

The previous prime is 21418157. The next prime is 21418183. The reversal of 21418164 is 46181412.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 48127 + ... + 48569.

It is an arithmetic number, because the mean of its divisors is an integer number (808080).

Almost surely, 2^21418164 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21418164, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29090880).

21418164 is an abundant number, since it is smaller than the sum of its proper divisors (36763596).

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

21418164 is a wasteful number, since it uses less digits than its factorization.

21418164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 549 (or 544 counting only the distinct ones).

The product of its digits is 1536, while the sum is 27.

The square root of 21418164 is about 4627.9762315725. The cubic root of 21418164 is about 277.7116379183.

Adding to 21418164 its reverse (46181412), we get a palindrome (67599576).

The spelling of 21418164 in words is "twenty-one million, four hundred eighteen thousand, one hundred sixty-four".