21118356391 has 6 divisors (see below), whose sum is σ = 23212738976. Its totient is φ = 19198505700.

The previous prime is 21118356353. The next prime is 21118356421. The reversal of 21118356391 is 19365381112.

It is not a de Polignac number, because 21118356391 - 2⁹ = 21118355879 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21118356991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 87265815 + ... + 87266056.

Almost surely, 2^21118356391 is an apocalyptic number.

21118356391 is a deficient number, since it is larger than the sum of its proper divisors (2094382585).

21118356391 is a wasteful number, since it uses less digits than its factorization.

21118356391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174531893 (or 174531882 counting only the distinct ones).

The product of its digits is 38880, while the sum is 40.

The spelling of 21118356391 in words is "twenty-one billion, one hundred eighteen million, three hundred fifty-six thousand, three hundred ninety-one".