21513330 has 128 divisors (see below), whose sum is σ = 62726400. Its totient is φ = 5225472.

The previous prime is 21513329. The next prime is 21513361. The reversal of 21513330 is 3331512.

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

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 197316 + ... + 197424.

It is an arithmetic number, because the mean of its divisors is an integer number (490050).

Almost surely, 2^21513330 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21513330, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31363200).

21513330 is an abundant number, since it is smaller than the sum of its proper divisors (41213070).

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

21513330 is a wasteful number, since it uses less digits than its factorization.

21513330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185 (or 179 counting only the distinct ones).

The product of its (nonzero) digits is 270, while the sum is 18.

The square root of 21513330 is about 4638.2464358850. The cubic root of 21513330 is about 278.1223431973.

Adding to 21513330 its reverse (3331512), we get a palindrome (24844842).

The spelling of 21513330 in words is "twenty-one million, five hundred thirteen thousand, three hundred thirty".