21078424 has 16 divisors (see below), whose sum is σ = 39825720. Its totient is φ = 10458240.

The previous prime is 21078403. The next prime is 21078427. The reversal of 21078424 is 42487012.

It is a junction number, because it is equal to n+sod(n) for n = 21078392 and 21078401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21078427) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9009 + ... + 11104.

Almost surely, 2^21078424 is an apocalyptic number.

It is an amenable number.

21078424 is a deficient number, since it is larger than the sum of its proper divisors (18747296).

21078424 is a wasteful number, since it uses less digits than its factorization.

21078424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20250 (or 20246 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 28.

The square root of 21078424 is about 4591.1244809959. The cubic root of 21078424 is about 276.2354288910.

The spelling of 21078424 in words is "twenty-one million, seventy-eight thousand, four hundred twenty-four".