21820284 has 108 divisors (see below), whose sum is σ = 61575696. Its totient is φ = 6500736.

The previous prime is 21820283. The next prime is 21820297. The reversal of 21820284 is 48202812.

It is a super-2 number, since 2×21820284² = 952249587681312, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820283) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 298872 + ... + 298944.

Almost surely, 2^21820284 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 21820284, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30787848).

21820284 is an abundant number, since it is smaller than the sum of its proper divisors (39755412).

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

21820284 is a wasteful number, since it uses less digits than its factorization.

21820284 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144 (or 120 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 21820284 is about 4671.2186846689. The cubic root of 21820284 is about 279.4388591765.

It can be divided in two parts, 218 and 20284, that added together give a palindrome (20502).

The spelling of 21820284 in words is "twenty-one million, eight hundred twenty thousand, two hundred eighty-four".