21438288 has 60 divisors (see below), whose sum is σ = 61151220. Its totient is φ = 7011264.

The previous prime is 21438283. The next prime is 21438301. The reversal of 21438288 is 88283412.

It is a happy number.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 9659664 + 11778624 = 3108^2 + 3432^2 .

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438283) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 404470 + ... + 404522.

It is an arithmetic number, because the mean of its divisors is an integer number (1019187).

Almost surely, 2^21438288 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 21438288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30575610).

21438288 is an abundant number, since it is smaller than the sum of its proper divisors (39712932).

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

21438288 is an frugal number, since it uses more digits than its factorization.

21438288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173 (or 58 counting only the distinct ones).

The product of its digits is 24576, while the sum is 36.

The square root of 21438288 is about 4630.1498895824. The cubic root of 21438288 is about 277.7985877861.

The spelling of 21438288 in words is "twenty-one million, four hundred thirty-eight thousand, two hundred eighty-eight".