21016320 has 144 divisors (see below), whose sum is σ = 72455712. Its totient is φ = 5160960.

The previous prime is 21016309. The next prime is 21016381. The reversal of 21016320 is 2361012.

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

It is a zygodrome in base 4.

It is a self number, because there is not a number n which added to its sum of digits gives 21016320.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49710 + ... + 50130.

Almost surely, 2^21016320 is an apocalyptic number.

21016320 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 21016320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36227856).

21016320 is an abundant number, since it is smaller than the sum of its proper divisors (51439392).

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

21016320 is a wasteful number, since it uses less digits than its factorization.

21016320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 458 (or 444 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21016320 is about 4584.3560071181. The cubic root of 21016320 is about 275.9638684061.

Adding to 21016320 its reverse (2361012), we get a palindrome (23377332).

The spelling of 21016320 in words is "twenty-one million, sixteen thousand, three hundred twenty".