21233520 has 240 divisors, whose sum is σ = 89137152. Its totient is φ = 4400640.

The previous prime is 21233503. The next prime is 21233579. The reversal of 21233520 is 2533212.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21233493 and 21233502.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 55249 + ... + 55631.

Almost surely, 2^21233520 is an apocalyptic number.

21233520 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 21233520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44568576).

21233520 is an abundant number, since it is smaller than the sum of its proper divisors (67903632).

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

21233520 is a wasteful number, since it uses less digits than its factorization.

21233520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420 (or 411 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21233520 is about 4607.9843749735. The cubic root of 21233520 is about 276.9112915212.

Adding to 21233520 its reverse (2533212), we get a palindrome (23766732).

The spelling of 21233520 in words is "twenty-one million, two hundred thirty-three thousand, five hundred twenty".