21000220 has 12 divisors (see below), whose sum is σ = 44100504. Its totient is φ = 8400080.

The previous prime is 21000193. The next prime is 21000229. The reversal of 21000220 is 2200012.

It is a happy number.

21000220 is an esthetic number in base 9, because in such base its adjacent digits differ by 1.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 524986 + ... + 525025.

It is an arithmetic number, because the mean of its divisors is an integer number (3675042).

Almost surely, 2^21000220 is an apocalyptic number.

21000220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000220 is an abundant number, since it is smaller than the sum of its proper divisors (23100284).

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

21000220 is a wasteful number, since it uses less digits than its factorization.

21000220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1050020 (or 1050018 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 7.

The square root of 21000220 is about 4582.5996988609. The cubic root of 21000220 is about 275.8933810686.

Adding to 21000220 its reverse (2200012), we get a palindrome (23200232).

The spelling of 21000220 in words is "twenty-one million, two hundred twenty", and thus it is an aban number.