21404412 has 108 divisors (see below), whose sum is σ = 60188856. Its totient is φ = 6648480.

The previous prime is 21404399. The next prime is 21404413. The reversal of 21404412 is 21440412.

It is a tau number, because it is divible by the number of its divisors (108).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404413) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 350862 + ... + 350922.

Almost surely, 2^21404412 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 21404412, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30094428).

21404412 is an abundant number, since it is smaller than the sum of its proper divisors (38784444).

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

21404412 is a wasteful number, since it uses less digits than its factorization.

21404412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118 (or 85 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 21404412 is about 4626.4902463963. The cubic root of 21404412 is about 277.6521882519.

Adding to 21404412 its reverse (21440412), we get a palindrome (42844824).

The spelling of 21404412 in words is "twenty-one million, four hundred four thousand, four hundred twelve".