21403424 has 96 divisors (see below), whose sum is σ = 52254720. Its totient is φ = 8425728.

The previous prime is 21403399. The next prime is 21403433. The reversal of 21403424 is 42430412.

It is a junction number, because it is equal to n+sod(n) for n = 21403396 and 21403405.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 199979 + ... + 200085.

It is an arithmetic number, because the mean of its divisors is an integer number (544320).

Almost surely, 2^21403424 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21403424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26127360).

21403424 is an abundant number, since it is smaller than the sum of its proper divisors (30851296).

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

21403424 is a wasteful number, since it uses less digits than its factorization.

21403424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190 (or 182 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 21403424 is about 4626.3834687583. The cubic root of 21403424 is about 277.6479161641.

Adding to 21403424 its reverse (42430412), we get a palindrome (63833836).

The spelling of 21403424 in words is "twenty-one million, four hundred three thousand, four hundred twenty-four".