21212532 has 144 divisors (see below), whose sum is σ = 65100672. Its totient is φ = 5744640.

The previous prime is 21212519. The next prime is 21212537. The reversal of 21212532 is 23521212.

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 (21212537) 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 47 ways as a sum of consecutive naturals, for example, 154768 + ... + 154904.

It is an arithmetic number, because the mean of its divisors is an integer number (452088).

Almost surely, 2^21212532 is an apocalyptic number.

21212532 is a gapful number since it is divisible by the number (22) 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 21212532, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32550336).

21212532 is an abundant number, since it is smaller than the sum of its proper divisors (43888140).

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

21212532 is a wasteful number, since it uses less digits than its factorization.

21212532 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198 (or 193 counting only the distinct ones).

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

The square root of 21212532 is about 4605.7064604684. The cubic root of 21212532 is about 276.8200249749.

Adding to 21212532 its reverse (23521212), we get a palindrome (44733744).

The spelling of 21212532 in words is "twenty-one million, two hundred twelve thousand, five hundred thirty-two".