21749328 has 60 divisors (see below), whose sum is σ = 61731540. Its totient is φ = 7147008.

The previous prime is 21749323. The next prime is 21749353. The reversal of 21749328 is 82394712.

It can be written as a sum of positive squares in 2 ways, for example, as 7551504 + 14197824 = 2748^2 + 3768^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21749292 and 21749301.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21749323) 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 11 ways as a sum of consecutive naturals, for example, 9478 + ... + 11546.

It is an arithmetic number, because the mean of its divisors is an integer number (1028859).

Almost surely, 2^21749328 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 21749328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30865770).

21749328 is an abundant number, since it is smaller than the sum of its proper divisors (39982212).

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

21749328 is a wasteful number, since it uses less digits than its factorization.

21749328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2156 (or 2147 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21749328 is about 4663.6174800256. The cubic root of 21749328 is about 279.1356337475.

The spelling of 21749328 in words is "twenty-one million, seven hundred forty-nine thousand, three hundred twenty-eight".