21421320 has 64 divisors (see below), whose sum is σ = 64782720. Its totient is φ = 5666304.

The previous prime is 21421319. The next prime is 21421333. The reversal of 21421320 is 2312412.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21421320.

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 15 ways as a sum of consecutive naturals, for example, 15789 + ... + 17091.

It is an arithmetic number, because the mean of its divisors is an integer number (1012230).

Almost surely, 2^21421320 is an apocalyptic number.

21421320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21421320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32391360).

21421320 is an abundant number, since it is smaller than the sum of its proper divisors (43361400).

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

21421320 is a wasteful number, since it uses less digits than its factorization.

21421320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1454 (or 1450 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21421320 is about 4628.3171887847. The cubic root of 21421320 is about 277.7252776633.

Adding to 21421320 its reverse (2312412), we get a palindrome (23733732).

The spelling of 21421320 in words is "twenty-one million, four hundred twenty-one thousand, three hundred twenty".