21242420 has 12 divisors (see below), whose sum is σ = 44609124. Its totient is φ = 8496960.

The previous prime is 21242393. The next prime is 21242443. The reversal of 21242420 is 2424212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13278736 + 7963684 = 3644^2 + 2822^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 531041 + ... + 531080.

It is an arithmetic number, because the mean of its divisors is an integer number (3717427).

Almost surely, 2^21242420 is an apocalyptic number.

21242420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21242420 is an abundant number, since it is smaller than the sum of its proper divisors (23366704).

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

21242420 is a wasteful number, since it uses less digits than its factorization.

21242420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1062130 (or 1062128 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 21242420 is about 4608.9499888803. The cubic root of 21242420 is about 276.9499751096.

Adding to 21242420 its reverse (2424212), we get a palindrome (23666632).

The spelling of 21242420 in words is "twenty-one million, two hundred forty-two thousand, four hundred twenty".