21326561280 has 320 divisors, whose sum is σ = 76506083280. Its totient is φ = 5683544064.

The previous prime is 21326561273. The next prime is 21326561339. The reversal of 21326561280 is 8216562312.

21326561280 is a `hidden beast` number, since 2 + 1 + 32 + 6 + 5 + 612 + 8 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (320).

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 19 ways as a sum of consecutive naturals, for example, 13270237 + ... + 13271843.

Almost surely, 2^21326561280 is an apocalyptic number.

21326561280 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 21326561280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38253041640).

21326561280 is an abundant number, since it is smaller than the sum of its proper divisors (55179522000).

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

21326561280 is an frugal number, since it uses more digits than its factorization.

21326561280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1654 (or 1617 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The spelling of 21326561280 in words is "twenty-one billion, three hundred twenty-six million, five hundred sixty-one thousand, two hundred eighty".