21718228 has 48 divisors (see below), whose sum is σ = 45416448. Its totient is φ = 8892000.

The previous prime is 21718201. The next prime is 21718241. The reversal of 21718228 is 82281712.

It is a Smith number, since the sum of its digits (31) 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 (31).

It is a self number, because there is not a number n which added to its sum of digits gives 21718228.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 113613 + ... + 113803.

It is an arithmetic number, because the mean of its divisors is an integer number (946176).

Almost surely, 2^21718228 is an apocalyptic number.

21718228 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21718228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22708224).

21718228 is an abundant number, since it is smaller than the sum of its proper divisors (23698220).

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

21718228 is a wasteful number, since it uses less digits than its factorization.

21718228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364 (or 362 counting only the distinct ones).

The product of its digits is 3584, while the sum is 31.

The square root of 21718228 is about 4660.2819657184. The cubic root of 21718228 is about 279.0025222127.

The spelling of 21718228 in words is "twenty-one million, seven hundred eighteen thousand, two hundred twenty-eight".