21420424 has 16 divisors (see below), whose sum is σ = 40273920. Its totient is φ = 10680720.

The previous prime is 21420403. The next prime is 21420433. The reversal of 21420424 is 42402412.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 432 + ... + 6559.

It is an arithmetic number, because the mean of its divisors is an integer number (2517120).

Almost surely, 2^21420424 is an apocalyptic number.

It is an amenable number.

21420424 is a deficient number, since it is larger than the sum of its proper divisors (18853496).

21420424 is a wasteful number, since it uses less digits than its factorization.

21420424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7380 (or 7376 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 19.

The square root of 21420424 is about 4628.2203923322. The cubic root of 21420424 is about 277.7214054257.

Adding to 21420424 its reverse (42402412), we get a palindrome (63822836).

The spelling of 21420424 in words is "twenty-one million, four hundred twenty thousand, four hundred twenty-four".