21891125880 has 512 divisors, whose sum is σ = 83462400000. Its totient is φ = 5059252224.

The previous prime is 21891125783. The next prime is 21891125903. The reversal of 21891125880 is 8852119812.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 36545821 + ... + 36546419.

It is an arithmetic number, because the mean of its divisors is an integer number (163012500).

Almost surely, 2^21891125880 is an apocalyptic number.

21891125880 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 21891125880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41731200000).

21891125880 is an abundant number, since it is smaller than the sum of its proper divisors (61571274120).

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

21891125880 is a wasteful number, since it uses less digits than its factorization.

21891125880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 788 (or 778 counting only the distinct ones).

The product of its (nonzero) digits is 92160, while the sum is 45.

The spelling of 21891125880 in words is "twenty-one billion, eight hundred ninety-one million, one hundred twenty-five thousand, eight hundred eighty".