21278536081920 has 1600 divisors, whose sum is σ = 87306348286080. Its totient is φ = 4909817659392.

The previous prime is 21278536081861. The next prime is 21278536081987. The reversal of 21278536081920 is 2918063587212.

21278536081920 is a `hidden beast` number, since 2 + 1 + 2 + 7 + 8 + 5 + 3 + 608 + 1 + 9 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 4968136099 + ... + 4968140381.

Almost surely, 2^{21278536081920} is an apocalyptic number.

21278536081920 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 21278536081920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43653174143040).

21278536081920 is an abundant number, since it is smaller than the sum of its proper divisors (66027812204160).

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

21278536081920 is a wasteful number, since it uses less digits than its factorization.

21278536081920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4447 (or 4422 counting only the distinct ones).

The product of its (nonzero) digits is 2903040, while the sum is 54.

The spelling of 21278536081920 in words is "twenty-one trillion, two hundred seventy-eight billion, five hundred thirty-six million, eighty-one thousand, nine hundred twenty".