21909396 has 48 divisors (see below), whose sum is σ = 54492480. Its totient is φ = 6827520.

The previous prime is 21909389. The next prime is 21909401. The reversal of 21909396 is 69390912.

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 (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42790 + ... + 43298.

It is an arithmetic number, because the mean of its divisors is an integer number (1135260).

Almost surely, 2^21909396 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 21909396, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27246240).

21909396 is an abundant number, since it is smaller than the sum of its proper divisors (32583084).

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

21909396 is a wasteful number, since it uses less digits than its factorization.

21909396 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 744 (or 742 counting only the distinct ones).

The product of its (nonzero) digits is 26244, while the sum is 39.

The square root of 21909396 is about 4680.7473762210. The cubic root of 21909396 is about 279.8187432338.

The spelling of 21909396 in words is "twenty-one million, nine hundred nine thousand, three hundred ninety-six".