21820208 has 20 divisors (see below), whose sum is σ = 44502360. Its totient is φ = 10335744.

The previous prime is 21820207. The next prime is 21820213. The reversal of 21820208 is 80202812.

It is a super-2 number, since 2×21820208² = 952242954326528, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21820207) 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, 35585 + ... + 36192.

It is an arithmetic number, because the mean of its divisors is an integer number (2225118).

Almost surely, 2^21820208 is an apocalyptic number.

It is an amenable number.

21820208 is an abundant number, since it is smaller than the sum of its proper divisors (22682152).

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

21820208 is a wasteful number, since it uses less digits than its factorization.

21820208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71804 (or 71798 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 23.

The square root of 21820208 is about 4671.2105497398. The cubic root of 21820208 is about 279.4385347478.

The spelling of 21820208 in words is "twenty-one million, eight hundred twenty thousand, two hundred eight".