21431424 has 192 divisors, whose sum is σ = 71163360. Its totient is φ = 5677056.

The previous prime is 21431401. The next prime is 21431489. The reversal of 21431424 is 42413412.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (21).

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

Its product of digits (768) is a multiple of the sum of its prime divisors (96).

It is a self number, because there is not a number n which added to its sum of digits gives 21431424.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 319839 + ... + 319905.

Almost surely, 2^21431424 is an apocalyptic number.

21431424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21431424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35581680).

21431424 is an abundant number, since it is smaller than the sum of its proper divisors (49731936).

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

21431424 is a wasteful number, since it uses less digits than its factorization.

21431424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115 (or 96 counting only the distinct ones).

The product of its digits is 768, while the sum is 21.

The square root of 21431424 is about 4629.4086015386. The cubic root of 21431424 is about 277.7689365838.

Adding to 21431424 its reverse (42413412), we get a palindrome (63844836).

The spelling of 21431424 in words is "twenty-one million, four hundred thirty-one thousand, four hundred twenty-four".