21203424 has 192 divisors, whose sum is σ = 71124480. Its totient is φ = 6082560.

The previous prime is 21203419. The next prime is 21203431. The reversal of 21203424 is 42430212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21203397 and 21203406.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 218544 + ... + 218640.

It is an arithmetic number, because the mean of its divisors is an integer number (370440).

Almost surely, 2^21203424 is an apocalyptic number.

21203424 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 21203424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35562240).

21203424 is an abundant number, since it is smaller than the sum of its proper divisors (49921056).

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

21203424 is a wasteful number, since it uses less digits than its factorization.

21203424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150 (or 136 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21203424 is about 4604.7175809163. The cubic root of 21203424 is about 276.7804000066.

Adding to 21203424 its reverse (42430212), we get a palindrome (63633636).

The spelling of 21203424 in words is "twenty-one million, two hundred three thousand, four hundred twenty-four".