216821540880 has 320 divisors, whose sum is σ = 854131998720. Its totient is φ = 49523664384.

The previous prime is 216821540861. The next prime is 216821540909. The reversal of 216821540880 is 88045128612.

216821540880 is a `hidden beast` number, since 2 + 1 + 6 + 8 + 21 + 540 + 8 + 80 = 666.

It is a Cunningham number, because it is equal to 465641²-1.

It is a super-2 number, since 2×216821540880² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 25140249 + ... + 25148871.

It is an arithmetic number, because the mean of its divisors is an integer number (2669162496).

Almost surely, 2^216821540880 is an apocalyptic number.

216821540880 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 216821540880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (427065999360).

216821540880 is an abundant number, since it is smaller than the sum of its proper divisors (637310457840).

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

216821540880 is a wasteful number, since it uses less digits than its factorization.

216821540880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10315 (or 10303 counting only the distinct ones).

The product of its (nonzero) digits is 245760, while the sum is 45.

The spelling of 216821540880 in words is "two hundred sixteen billion, eight hundred twenty-one million, five hundred forty thousand, eight hundred eighty".