21220128 has 36 divisors (see below), whose sum is σ = 60345558. Its totient is φ = 7073280.

The previous prime is 21220109. The next prime is 21220153. The reversal of 21220128 is 82102212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20684304 + 535824 = 4548^2 + 732^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a self number, because there is not a number n which added to its sum of digits gives 21220128.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36553 + ... + 37128.

Almost surely, 2^21220128 is an apocalyptic number.

It is an amenable number.

21220128 is an abundant number, since it is smaller than the sum of its proper divisors (39125430).

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

21220128 is a wasteful number, since it uses less digits than its factorization.

21220128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73697 (or 73686 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 21220128 is about 4606.5310158513. The cubic root of 21220128 is about 276.8530632118.

The spelling of 21220128 in words is "twenty-one million, two hundred twenty thousand, one hundred twenty-eight".