21658428 has 120 divisors (see below), whose sum is σ = 63423360. Its totient is φ = 6389280.

The previous prime is 21658421. The next prime is 21658457. The reversal of 21658428 is 82485612.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21658392 and 21658401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21658421) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 210225 + ... + 210327.

It is an arithmetic number, because the mean of its divisors is an integer number (528528).

Almost surely, 2^21658428 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 21658428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31711680).

21658428 is an abundant number, since it is smaller than the sum of its proper divisors (41764932).

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

21658428 is a wasteful number, since it uses less digits than its factorization.

21658428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189 (or 178 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 21658428 is about 4653.8616223519. The cubic root of 21658428 is about 278.7462138948.

It can be divided in two parts, 216584 and 28, that added together give a palindrome (216612).

The spelling of 21658428 in words is "twenty-one million, six hundred fifty-eight thousand, four hundred twenty-eight".