21916173493 has 4 divisors (see below), whose sum is σ = 21916576300. Its totient is φ = 21915770688.

The previous prime is 21916173463. The next prime is 21916173533. The reversal of 21916173493 is 39437161912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6281672049 + 15634501444 = 79257^2 + 125038^2 .

It is a cyclic number.

It is not a de Polignac number, because 21916173493 - 2²⁵ = 21882619061 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 (21916173413) 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, 104130 + ... + 233827.

It is an arithmetic number, because the mean of its divisors is an integer number (5479144075).

Almost surely, 2^21916173493 is an apocalyptic number.

It is an amenable number.

21916173493 is a deficient number, since it is larger than the sum of its proper divisors (402807).

21916173493 is an equidigital number, since it uses as much as digits as its factorization.

21916173493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 402806.

The product of its digits is 244944, while the sum is 46.

The spelling of 21916173493 in words is "twenty-one billion, nine hundred sixteen million, one hundred seventy-three thousand, four hundred ninety-three".