21109920 has 192 divisors, whose sum is σ = 76204800. Its totient is φ = 4866048.

The previous prime is 21109901. The next prime is 21109927. The reversal of 21109920 is 2990112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is not an unprimeable number, because it can be changed into a prime (21109927) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 105981 + ... + 106179.

It is an arithmetic number, because the mean of its divisors is an integer number (396900).

Almost surely, 2^21109920 is an apocalyptic number.

21109920 is a gapful number since it is divisible by the number (20) 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 21109920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38102400).

21109920 is an abundant number, since it is smaller than the sum of its proper divisors (55094880).

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

21109920 is a wasteful number, since it uses less digits than its factorization.

21109920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 239 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 24.

The square root of 21109920 is about 4594.5532971117. The cubic root of 21109920 is about 276.3729467819.

The spelling of 21109920 in words is "twenty-one million, one hundred nine thousand, nine hundred twenty".