21909280 has 48 divisors (see below), whose sum is σ = 54492480. Its totient is φ = 8301312.

The previous prime is 21909269. The next prime is 21909287. The reversal of 21909280 is 8290912.

It is not an unprimeable number, because it can be changed into a prime (21909287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 564 + ... + 6643.

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

Almost surely, 2^21909280 is an apocalyptic number.

21909280 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 21909280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27246240).

21909280 is an abundant number, since it is smaller than the sum of its proper divisors (32583200).

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

21909280 is a wasteful number, since it uses less digits than its factorization.

21909280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7241 (or 7233 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 21909280 is about 4680.7349850210. The cubic root of 21909280 is about 279.8182493965.

The spelling of 21909280 in words is "twenty-one million, nine hundred nine thousand, two hundred eighty".