21621432 has 128 divisors (see below), whose sum is σ = 65640960. Its totient is φ = 5806080.

The previous prime is 21621427. The next prime is 21621437. The reversal of 21621432 is 23412612.

It is an interprime number because it is at equal distance from previous prime (21621427) and next prime (21621437).

It is a Harshad number since it is a multiple of its sum of digits (21).

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

It is a junction number, because it is equal to n+sod(n) for n = 21621399 and 21621408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621437) 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 31 ways as a sum of consecutive naturals, for example, 296148 + ... + 296220.

It is an arithmetic number, because the mean of its divisors is an integer number (512820).

Almost surely, 2^21621432 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 21621432, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32820480).

21621432 is an abundant number, since it is smaller than the sum of its proper divisors (44019528).

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

21621432 is a wasteful number, since it uses less digits than its factorization.

21621432 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173 (or 169 counting only the distinct ones).

The product of its digits is 576, while the sum is 21.

The square root of 21621432 is about 4649.8851598722. The cubic root of 21621432 is about 278.5874093208.

The spelling of 21621432 in words is "twenty-one million, six hundred twenty-one thousand, four hundred thirty-two".