21809412 has 60 divisors (see below), whose sum is σ = 57772176. Its totient is φ = 7173360.

The previous prime is 21809401. The next prime is 21809413. The reversal of 21809412 is 21490812.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21809413) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 26487 + ... + 27297.

Almost surely, 2^21809412 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 21809412, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28886088).

21809412 is an abundant number, since it is smaller than the sum of its proper divisors (35962764).

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

21809412 is a wasteful number, since it uses less digits than its factorization.

21809412 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 910 (or 899 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 21809412 is about 4670.0548176654. The cubic root of 21809412 is about 279.3924411435.

The spelling of 21809412 in words is "twenty-one million, eight hundred nine thousand, four hundred twelve".