21533128 has 8 divisors (see below), whose sum is σ = 40374630. Its totient is φ = 10766560.

The previous prime is 21533123. The next prime is 21533131. The reversal of 21533128 is 82133512.

It can be written as a sum of positive squares in only one way, i.e., 20088324 + 1444804 = 4482^2 + 1202^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (21533123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1345813 + ... + 1345828.

Almost surely, 2^21533128 is an apocalyptic number.

It is an amenable number.

21533128 is a deficient number, since it is larger than the sum of its proper divisors (18841502).

21533128 is a wasteful number, since it uses less digits than its factorization.

21533128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2691647 (or 2691643 counting only the distinct ones).

The product of its digits is 1440, while the sum is 25.

The square root of 21533128 is about 4640.3801568406. The cubic root of 21533128 is about 278.2076326114.

The spelling of 21533128 in words is "twenty-one million, five hundred thirty-three thousand, one hundred twenty-eight".