21138432 has 88 divisors (see below), whose sum is σ = 64455936. Its totient is φ = 6033408.

The previous prime is 21138427. The next prime is 21138437. The reversal of 21138432 is 23483112.

It is an interprime number because it is at equal distance from previous prime (21138427) and next prime (21138437).

It is a Harshad number since it is a multiple of its sum of digits (24).

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 (21138437) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21013 + ... + 21995.

Almost surely, 2^21138432 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 21138432, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32227968).

21138432 is an abundant number, since it is smaller than the sum of its proper divisors (43317504).

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

21138432 is an equidigital number, since it uses as much as digits as its factorization.

21138432 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1013 (or 995 counting only the distinct ones).

The product of its digits is 1152, while the sum is 24.

The square root of 21138432 is about 4597.6550544816. The cubic root of 21138432 is about 276.4973180167.

The spelling of 21138432 in words is "twenty-one million, one hundred thirty-eight thousand, four hundred thirty-two".