21811121280 has 384 divisors, whose sum is σ = 81653382720. Its totient is φ = 5332967424.

The previous prime is 21811121257. The next prime is 21811121333. The reversal of 21811121280 is 8212111812.

It is a tau number, because it is divible by the number of its divisors (384).

It is a super-2 number, since 2×21811121280² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12204547 + ... + 12206333.

Almost surely, 2^21811121280 is an apocalyptic number.

21811121280 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 21811121280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40826691360).

21811121280 is an abundant number, since it is smaller than the sum of its proper divisors (59842261440).

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

21811121280 is a wasteful number, since it uses less digits than its factorization.

21811121280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1988 (or 1973 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 27.

The spelling of 21811121280 in words is "twenty-one billion, eight hundred eleven million, one hundred twenty-one thousand, two hundred eighty".