21424520 has 32 divisors (see below), whose sum is σ = 51914520. Its totient is φ = 7910400.

The previous prime is 21424511. The next prime is 21424547. The reversal of 21424520 is 2542412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 17123044 + 4301476 = 4138^2 + 2074^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21424492 and 21424501.

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, 20081 + ... + 21120.

Almost surely, 2^21424520 is an apocalyptic number.

21424520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21424520 is an abundant number, since it is smaller than the sum of its proper divisors (30490000).

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

21424520 is a wasteful number, since it uses less digits than its factorization.

21424520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41225 (or 41221 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21424520 is about 4628.6628738762. The cubic root of 21424520 is about 277.7391062017.

Adding to 21424520 its reverse (2542412), we get a palindrome (23966932).

It can be divided in two parts, 214245 and 20, that multiplied together give a square (4284900 = 2070²).

The spelling of 21424520 in words is "twenty-one million, four hundred twenty-four thousand, five hundred twenty".