21128424 has 32 divisors (see below), whose sum is σ = 52933920. Its totient is φ = 7027776.

The previous prime is 21128411. The next prime is 21128441. The reversal of 21128424 is 42482112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21128394 and 21128403.

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, 20694 + ... + 21690.

It is an arithmetic number, because the mean of its divisors is an integer number (1654185).

Almost surely, 2^21128424 is an apocalyptic number.

21128424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21128424 is an abundant number, since it is smaller than the sum of its proper divisors (31805496).

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

21128424 is a wasteful number, since it uses less digits than its factorization.

21128424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1889 (or 1885 counting only the distinct ones).

The product of its digits is 1024, while the sum is 24.

The square root of 21128424 is about 4596.5665447157. The cubic root of 21128424 is about 276.4536752025.

The spelling of 21128424 in words is "twenty-one million, one hundred twenty-eight thousand, four hundred twenty-four".