21815801280 has 672 divisors, whose sum is σ = 95805126144. Its totient is φ = 4601401344.

The previous prime is 21815801239. The next prime is 21815801317. The reversal of 21815801280 is 8210851812.

It is a tau number, because it is divible by the number of its divisors (672).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 7074619 + ... + 7077701.

It is an arithmetic number, because the mean of its divisors is an integer number (142567152).

Almost surely, 2^21815801280 is an apocalyptic number.

21815801280 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 21815801280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47902563072).

21815801280 is an abundant number, since it is smaller than the sum of its proper divisors (73989324864).

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

21815801280 is a wasteful number, since it uses less digits than its factorization.

21815801280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3135 (or 3113 counting only the distinct ones).

The product of its (nonzero) digits is 10240, while the sum is 36.

The spelling of 21815801280 in words is "twenty-one billion, eight hundred fifteen million, eight hundred one thousand, two hundred eighty".