21729344 has 126 divisors (see below), whose sum is σ = 55638954. Its totient is φ = 8386560.

The previous prime is 21729341. The next prime is 21729361. The reversal of 21729344 is 44392712.

It can be written as a sum of positive squares in 3 ways, for example, as 1658944 + 20070400 = 1288^2 + 4480^2 .

It is a Harshad number since it is a multiple of its sum of digits (32).

Its product of digits (12096) is a multiple of the sum of its prime divisors (63).

It is a self number, because there is not a number n which added to its sum of digits gives 21729344.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729341) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 529964 + ... + 530004.

It is an arithmetic number, because the mean of its divisors is an integer number (441579).

Almost surely, 2^21729344 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 21729344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27819477).

21729344 is an abundant number, since it is smaller than the sum of its proper divisors (33909610).

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

21729344 is a wasteful number, since it uses less digits than its factorization.

21729344 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 63 counting only the distinct ones).

The product of its digits is 12096, while the sum is 32.

The square root of 21729344 is about 4661.4744448511. The cubic root of 21729344 is about 279.0501145402.

The spelling of 21729344 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred forty-four".