21633012 has 72 divisors (see below), whose sum is σ = 57057000. Its totient is φ = 6905088.

The previous prime is 21633011. The next prime is 21633023. The reversal of 21633012 is 21033612.

21633012 is a `hidden beast` number, since 21 + 633 + 0 + 12 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 5035536 + 16597476 = 2244^2 + 4074^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21633011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 145114 + ... + 145262.

Almost surely, 2^21633012 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21633012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28528500).

21633012 is an abundant number, since it is smaller than the sum of its proper divisors (35423988).

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

21633012 is a wasteful number, since it uses less digits than its factorization.

21633012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 305 (or 300 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21633012 is about 4651.1301852346. The cubic root of 21633012 is about 278.6371356978.

Adding to 21633012 its reverse (21033612), we get a palindrome (42666624).

The spelling of 21633012 in words is "twenty-one million, six hundred thirty-three thousand, twelve".