21013121320 has 128 divisors (see below), whose sum is σ = 51372921600. Its totient is φ = 7704539136.

The previous prime is 21013121293. The next prime is 21013121323. The reversal of 21013121320 is 2312131012.

It is a junction number, because it is equal to n+sod(n) for n = 21013121294 and 21013121303.

It is not an unprimeable number, because it can be changed into a prime (21013121323) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12835542 + ... + 12837178.

It is an arithmetic number, because the mean of its divisors is an integer number (401350950).

Almost surely, 2^21013121320 is an apocalyptic number.

21013121320 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 21013121320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25686460800).

21013121320 is an abundant number, since it is smaller than the sum of its proper divisors (30359800280).

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

21013121320 is a wasteful number, since it uses less digits than its factorization.

21013121320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2147 (or 2143 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21013121320 its reverse (2312131012), we get a palindrome (23325252332).

The spelling of 21013121320 in words is "twenty-one billion, thirteen million, one hundred twenty-one thousand, three hundred twenty".