21251232 has 72 divisors (see below), whose sum is σ = 61061364. Its totient is φ = 7010304.

The previous prime is 21251201. The next prime is 21251239. The reversal of 21251232 is 23215212.

It can be written as a sum of positive squares in 2 ways, for example, as 16941456 + 4309776 = 4116^2 + 2076^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is a super-2 number, since 2×21251232² = 903229723035648, which contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21251239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32218 + ... + 32870.

Almost surely, 2^21251232 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 21251232, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30530682).

21251232 is an abundant number, since it is smaller than the sum of its proper divisors (39810132).

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

21251232 is a wasteful number, since it uses less digits than its factorization.

21251232 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 782 (or 771 counting only the distinct ones).

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

The square root of 21251232 is about 4609.9058558717. The cubic root of 21251232 is about 276.9882655648.

Adding to 21251232 its reverse (23215212), we get a palindrome (44466444).

The spelling of 21251232 in words is "twenty-one million, two hundred fifty-one thousand, two hundred thirty-two".