21351330 has 256 divisors, whose sum is σ = 77414400. Its totient is φ = 4043520.

The previous prime is 21351311. The next prime is 21351347. The reversal of 21351330 is 3315312.

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 127 ways as a sum of consecutive naturals, for example, 270231 + ... + 270309.

It is an arithmetic number, because the mean of its divisors is an integer number (302400).

Almost surely, 2^21351330 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21351330, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38707200).

21351330 is an abundant number, since it is smaller than the sum of its proper divisors (56063070).

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

21351330 is a wasteful number, since it uses less digits than its factorization.

21351330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126 (or 120 counting only the distinct ones).

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

The square root of 21351330 is about 4620.7499391333. The cubic root of 21351330 is about 277.4224765186.

Adding to 21351330 its reverse (3315312), we get a palindrome (24666642).

The spelling of 21351330 in words is "twenty-one million, three hundred fifty-one thousand, three hundred thirty".