21386813520 has 80 divisors (see below), whose sum is σ = 66437890560. Its totient is φ = 5691213312.

The previous prime is 21386813471. The next prime is 21386813521. The reversal of 21386813520 is 2531868312.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21386813521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21942 + ... + 207978.

It is an arithmetic number, because the mean of its divisors is an integer number (830473632).

Almost surely, 2^21386813520 is an apocalyptic number.

21386813520 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 21386813520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33218945280).

21386813520 is an abundant number, since it is smaller than the sum of its proper divisors (45051077040).

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

21386813520 is a wasteful number, since it uses less digits than its factorization.

21386813520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 186532 (or 186526 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 39.

The spelling of 21386813520 in words is "twenty-one billion, three hundred eighty-six million, eight hundred thirteen thousand, five hundred twenty".