21840424 has 16 divisors (see below), whose sum is σ = 43106400. Its totient is φ = 10345392.

The previous prime is 21840421. The next prime is 21840433. The reversal of 21840424 is 42404812.

It is not an unprimeable number, because it can be changed into a prime (21840421) 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, 71692 + ... + 71995.

It is an arithmetic number, because the mean of its divisors is an integer number (2694150).

Almost surely, 2^21840424 is an apocalyptic number.

It is an amenable number.

21840424 is a deficient number, since it is larger than the sum of its proper divisors (21265976).

21840424 is a wasteful number, since it uses less digits than its factorization.

21840424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143712 (or 143708 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 25.

The square root of 21840424 is about 4673.3739418112. The cubic root of 21840424 is about 279.5248062400.

The spelling of 21840424 in words is "twenty-one million, eight hundred forty thousand, four hundred twenty-four".