21220220 has 24 divisors (see below), whose sum is σ = 50928864. Its totient is φ = 7275456.

The previous prime is 21220219. The next prime is 21220223. The reversal of 21220220 is 2202212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75647 + ... + 75926.

It is an arithmetic number, because the mean of its divisors is an integer number (2122036).

Almost surely, 2^21220220 is an apocalyptic number.

21220220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21220220 is an abundant number, since it is smaller than the sum of its proper divisors (29708644).

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

21220220 is a wasteful number, since it uses less digits than its factorization.

21220220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151589 (or 151587 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 11.

The square root of 21220220 is about 4606.5410016627. The cubic root of 21220220 is about 276.8534633106.

Adding to 21220220 its reverse (2202212), we get a palindrome (23422432).

The spelling of 21220220 in words is "twenty-one million, two hundred twenty thousand, two hundred twenty".