21909888 has 384 divisors, whose sum is σ = 89107200. Its totient is φ = 4976640.

The previous prime is 21909887. The next prime is 21909911. The reversal of 21909888 is 88890912.

It is a tau number, because it is divible by the number of its divisors (384).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909887) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1153143 + ... + 1153161.

It is an arithmetic number, because the mean of its divisors is an integer number (232050).

Almost surely, 2^21909888 is an apocalyptic number.

21909888 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21909888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44553600).

21909888 is an abundant number, since it is smaller than the sum of its proper divisors (67197312).

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

21909888 is a wasteful number, since it uses less digits than its factorization.

21909888 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70 (or 55 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 45.

The square root of 21909888 is about 4680.7999316356. The cubic root of 21909888 is about 279.8208377657.

It can be divided in two parts, 21 and 909888, that added together give a palindrome (909909).

The spelling of 21909888 in words is "twenty-one million, nine hundred nine thousand, eight hundred eighty-eight".