21240450 has 144 divisors (see below), whose sum is σ = 71263296. Its totient is φ = 4406400.

The previous prime is 21240433. The next prime is 21240511. The reversal of 21240450 is 5404212.

21240450 is a `hidden beast` number, since 212 + 4 + 0 + 450 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 34344 + ... + 34956.

It is an arithmetic number, because the mean of its divisors is an integer number (494884).

Almost surely, 2^21240450 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21240450, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35631648).

21240450 is an abundant number, since it is smaller than the sum of its proper divisors (50022846).

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

21240450 is a wasteful number, since it uses less digits than its factorization.

21240450 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 649 (or 641 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21240450 is about 4608.7362693042. The cubic root of 21240450 is about 276.9414134938.

Adding to 21240450 its reverse (5404212), we get a palindrome (26644662).

It can be divided in two parts, 21 and 240450, that added together give a triangular number (240471 = T₆₉₃).

The spelling of 21240450 in words is "twenty-one million, two hundred forty thousand, four hundred fifty".