21008220 has 24 divisors (see below), whose sum is σ = 58823184. Its totient is φ = 5602176.

The previous prime is 21008219. The next prime is 21008237. The reversal of 21008220 is 2280012.

21008220 is nontrivially palindromic in base 14.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21008220.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175009 + ... + 175128.

It is an arithmetic number, because the mean of its divisors is an integer number (2450966).

Almost surely, 2^21008220 is an apocalyptic number.

21008220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21008220 is an abundant number, since it is smaller than the sum of its proper divisors (37814964).

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

21008220 is a wasteful number, since it uses less digits than its factorization.

21008220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350149 (or 350147 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 21008220 is about 4583.4724827362. The cubic root of 21008220 is about 275.9284103340.

Adding to 21008220 its reverse (2280012), we get a palindrome (23288232).

The spelling of 21008220 in words is "twenty-one million, eight thousand, two hundred twenty".