21128790 has 48 divisors (see below), whose sum is σ = 53889552. Its totient is φ = 5300736.

The previous prime is 21128777. The next prime is 21128797. The reversal of 21128790 is 9782112.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21128797) 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, 7452 + ... + 9888.

It is an arithmetic number, because the mean of its divisors is an integer number (1122699).

Almost surely, 2^21128790 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21128790, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26944776).

21128790 is an abundant number, since it is smaller than the sum of its proper divisors (32760762).

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

21128790 is a wasteful number, since it uses less digits than its factorization.

21128790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2481 (or 2464 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21128790 is about 4596.6063568681. The cubic root of 21128790 is about 276.4552714954.

The spelling of 21128790 in words is "twenty-one million, one hundred twenty-eight thousand, seven hundred ninety".