21020220 has 108 divisors (see below), whose sum is σ = 69143256. Its totient is φ = 5166720.

The previous prime is 21020161. The next prime is 21020227. The reversal of 21020220 is 2202012.

It is a super-3 number, since 3×21020220³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020227) 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, 30075 + ... + 30765.

Almost surely, 2^21020220 is an apocalyptic number.

21020220 is a gapful number since it is divisible by the number (20) 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 21020220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34571628).

21020220 is an abundant number, since it is smaller than the sum of its proper divisors (48123036).

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

21020220 is a wasteful number, since it uses less digits than its factorization.

21020220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732 (or 714 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 21020220 is about 4584.7813470219. The cubic root of 21020220 is about 275.9809375618.

Adding to 21020220 its reverse (2202012), we get a palindrome (23222232).

The spelling of 21020220 in words is "twenty-one million, twenty thousand, two hundred twenty".