21229128 has 60 divisors (see below), whose sum is σ = 59791545. Its totient is φ = 7037280.

The previous prime is 21229111. The next prime is 21229139. The reversal of 21229128 is 82192212.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 12830724 + 8398404 = 3582^2 + 2898^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3258.

It is a Harshad number since it is a multiple of its sum of digits (27).

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

It is an unprimeable number.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 117198 + ... + 117378.

Almost surely, 2^21229128 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 21229128

21229128 is an abundant number, since it is smaller than the sum of its proper divisors (38562417).

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

21229128 is an equidigital number, since it uses as much as digits as its factorization.

21229128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 380 (or 186 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21229128 is about 4607.5077862115. The cubic root of 21229128 is about 276.8921978389.

Multiplying 21229128 by its product of digits (1152), we get a square (24455955456 = 156384²).

The spelling of 21229128 in words is "twenty-one million, two hundred twenty-nine thousand, one hundred twenty-eight".