21135228 has 24 divisors (see below), whose sum is σ = 49674240. Its totient is φ = 6993840.

The previous prime is 21135227. The next prime is 21135259. The reversal of 21135228 is 82253112.

21135228 is nontrivially palindromic in base 14.

It is a super-2 number, since 2×21135228² = 893395725223968, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21135198 and 21135207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135223) 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, 4668 + ... + 8003.

It is an arithmetic number, because the mean of its divisors is an integer number (2069760).

Almost surely, 2^21135228 is an apocalyptic number.

It is an amenable number.

21135228 is an abundant number, since it is smaller than the sum of its proper divisors (28539012).

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

21135228 is a wasteful number, since it uses less digits than its factorization.

21135228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12817 (or 12815 counting only the distinct ones).

The product of its digits is 960, while the sum is 24.

The square root of 21135228 is about 4597.3066027839. The cubic root of 21135228 is about 276.4833475360.

The spelling of 21135228 in words is "twenty-one million, one hundred thirty-five thousand, two hundred twenty-eight".