21491788873728 has 68 divisors (see below), whose sum is σ = 57311000269328. Its totient is φ = 7163929559040.

The previous prime is 21491788873727. The next prime is 21491788873739. The reversal of 21491788873728 is 82737888719412.

It is a self number, because there is not a number n which added to its sum of digits gives 21491788873728.

It is not an unprimeable number, because it can be changed into a prime (21491788873721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 54459838 + ... + 54853053.

Almost surely, 2^{21491788873728} is an apocalyptic number.

It is an amenable number.

21491788873728 is an abundant number, since it is smaller than the sum of its proper divisors (35819211395600).

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

21491788873728 is an frugal number, since it uses more digits than its factorization.

21491788873728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109312926 (or 109312896 counting only the distinct ones).

The product of its digits is 606928896, while the sum is 75.

The spelling of 21491788873728 in words is "twenty-one trillion, four hundred ninety-one billion, seven hundred eighty-eight million, eight hundred seventy-three thousand, seven hundred twenty-eight".