21223680 has 72 divisors (see below), whose sum is σ = 67795392. Its totient is φ = 5658624.

The previous prime is 21223673. The next prime is 21223693. The reversal of 21223680 is 8632212.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21223680.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1077 + ... + 6603.

Almost surely, 2^21223680 is an apocalyptic number.

21223680 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 21223680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33897696).

21223680 is an abundant number, since it is smaller than the sum of its proper divisors (46571712).

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

21223680 is an equidigital number, since it uses as much as digits as its factorization.

21223680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5551 (or 5537 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21223680 is about 4606.9165392918. The cubic root of 21223680 is about 276.8685096662.

Adding to 21223680 its reverse (8632212), we get a palindrome (29855892).

The spelling of 21223680 in words is "twenty-one million, two hundred twenty-three thousand, six hundred eighty".