21206012520 has 512 divisors, whose sum is σ = 82798018560. Its totient is φ = 4216320000.

The previous prime is 21206012507. The next prime is 21206012561. The reversal of 21206012520 is 2521060212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 28930074 + ... + 28930806.

It is an arithmetic number, because the mean of its divisors is an integer number (161714880).

Almost surely, 2^21206012520 is an apocalyptic number.

21206012520 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 21206012520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41399009280).

21206012520 is an abundant number, since it is smaller than the sum of its proper divisors (61592006040).

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

21206012520 is a wasteful number, since it uses less digits than its factorization.

21206012520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 897 (or 893 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

Adding to 21206012520 its reverse (2521060212), we get a palindrome (23727072732).

The spelling of 21206012520 in words is "twenty-one billion, two hundred six million, twelve thousand, five hundred twenty".