21724132 has 12 divisors (see below), whose sum is σ = 39328380. Its totient is φ = 10487456.

The previous prime is 21724111. The next prime is 21724133. The reversal of 21724132 is 23142712.

It can be written as a sum of positive squares in 2 ways, for example, as 10394176 + 11329956 = 3224^2 + 3366^2 .

It is a super-2 number, since 2×21724132² = 943875822306848, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21724133) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 93523 + ... + 93754.

It is an arithmetic number, because the mean of its divisors is an integer number (3277365).

Almost surely, 2^21724132 is an apocalyptic number.

It is an amenable number.

21724132 is a deficient number, since it is larger than the sum of its proper divisors (17604248).

21724132 is a wasteful number, since it uses less digits than its factorization.

21724132 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187310 (or 187308 counting only the distinct ones).

The product of its digits is 672, while the sum is 22.

The square root of 21724132 is about 4660.9153607419. The cubic root of 21724132 is about 279.0278017713.

Adding to 21724132 its reverse (23142712), we get a palindrome (44866844).

The spelling of 21724132 in words is "twenty-one million, seven hundred twenty-four thousand, one hundred thirty-two".