21312252 has 108 divisors (see below), whose sum is σ = 60750144. Its totient is φ = 6289920.

The previous prime is 21312233. The next prime is 21312257. The reversal of 21312252 is 25221312.

It is a hoax number, since the sum of its digits (18) coincides with the sum of the digits of its distinct prime factors.

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 (21312257) 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 35 ways as a sum of consecutive naturals, for example, 188548 + ... + 188660.

Almost surely, 2^21312252 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 21312252, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30375072).

21312252 is an abundant number, since it is smaller than the sum of its proper divisors (39437892).

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

21312252 is a wasteful number, since it uses less digits than its factorization.

21312252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180 (or 162 counting only the distinct ones).

The product of its digits is 240, while the sum is 18.

The square root of 21312252 is about 4616.5194681708. The cubic root of 21312252 is about 277.2531235055.

Adding to 21312252 its reverse (25221312), we get a palindrome (46533564).

The spelling of 21312252 in words is "twenty-one million, three hundred twelve thousand, two hundred fifty-two".