21015450 has 60 divisors (see below), whose sum is σ = 58403070. Its totient is φ = 5603040.

The previous prime is 21015437. The next prime is 21015461. The reversal of 21015450 is 5451012.

21015450 is a `hidden beast` number, since 210 + 1 + 5 + 450 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 18122049 + 2893401 = 4257^2 + 1701^2 .

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 1456 + ... + 6644.

Almost surely, 2^21015450 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21015450, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29201535).

21015450 is an abundant number, since it is smaller than the sum of its proper divisors (37387620).

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

21015450 is a wasteful number, since it uses less digits than its factorization.

21015450 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5213 (or 5199 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21015450 is about 4584.2611182174. The cubic root of 21015450 is about 275.9600603832.

Adding to 21015450 its reverse (5451012), we get a palindrome (26466462).

The spelling of 21015450 in words is "twenty-one million, fifteen thousand, four hundred fifty".