21390881760 has 144 divisors (see below), whose sum is σ = 75700091376. Its totient is φ = 5704224768.

The previous prime is 21390881747. The next prime is 21390881767. The reversal of 21390881760 is 6718809312.

It is a tau number, because it is divible by the number of its divisors (144).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390881767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 236209 + ... + 313968.

It is an arithmetic number, because the mean of its divisors is an integer number (525695079).

Almost surely, 2^21390881760 is an apocalyptic number.

21390881760 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21390881760 is an abundant number, since it is smaller than the sum of its proper divisors (54309209616).

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

21390881760 is an equidigital number, since it uses as much as digits as its factorization.

21390881760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 550207 (or 550187 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The spelling of 21390881760 in words is "twenty-one billion, three hundred ninety million, eight hundred eighty-one thousand, seven hundred sixty".