21242220 has 24 divisors (see below), whose sum is σ = 59478384. Its totient is φ = 5664576.

The previous prime is 21242203. The next prime is 21242237. The reversal of 21242220 is 2224212.

It is an interprime number because it is at equal distance from previous prime (21242203) and next prime (21242237).

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 21242220.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176959 + ... + 177078.

It is an arithmetic number, because the mean of its divisors is an integer number (2478266).

Almost surely, 2^21242220 is an apocalyptic number.

21242220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21242220 is an abundant number, since it is smaller than the sum of its proper divisors (38236164).

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

21242220 is a wasteful number, since it uses less digits than its factorization.

21242220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 354049 (or 354047 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21242220 is about 4608.9282919134. The cubic root of 21242220 is about 276.9491059342.

Adding to 21242220 its reverse (2224212), we get a palindrome (23466432).

The spelling of 21242220 in words is "twenty-one million, two hundred forty-two thousand, two hundred twenty".