21671328 has 144 divisors (see below), whose sum is σ = 70326144. Its totient is φ = 5806080.

The previous prime is 21671327. The next prime is 21671333. The reversal of 21671328 is 82317612.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

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 = 21671295 and 21671304.

It is not an unprimeable number, because it can be changed into a prime (21671327) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 79833 + ... + 80103.

It is an arithmetic number, because the mean of its divisors is an integer number (488376).

Almost surely, 2^21671328 is an apocalyptic number.

21671328 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21671328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35163072).

21671328 is an abundant number, since it is smaller than the sum of its proper divisors (48654816).

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

21671328 is a wasteful number, since it uses less digits than its factorization.

21671328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 315 (or 300 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 21671328 is about 4655.2473618488. The cubic root of 21671328 is about 278.8015443570.

The spelling of 21671328 in words is "twenty-one million, six hundred seventy-one thousand, three hundred twenty-eight".