21004530 has 64 divisors (see below), whose sum is σ = 52531200. Its totient is φ = 5370624.

The previous prime is 21004517. The next prime is 21004541. The reversal of 21004530 is 3540012.

It is a Harshad number since it is a multiple of its sum of digits (15).

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, 140896 + ... + 141044.

It is an arithmetic number, because the mean of its divisors is an integer number (820800).

Almost surely, 2^21004530 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21004530, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26265600).

21004530 is an abundant number, since it is smaller than the sum of its proper divisors (31526670).

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

21004530 is a wasteful number, since it uses less digits than its factorization.

21004530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 323.

The product of its (nonzero) digits is 120, while the sum is 15.

The square root of 21004530 is about 4583.0699318252. The cubic root of 21004530 is about 275.9122541904.

Adding to 21004530 its reverse (3540012), we get a palindrome (24544542).

The spelling of 21004530 in words is "twenty-one million, four thousand, five hundred thirty".