26991342581 has 4 divisors (see below), whose sum is σ = 30847248672. Its totient is φ = 23135436492.

The previous prime is 26991342569. The next prime is 26991342583. The reversal of 26991342581 is 18524319962.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 26991342581 - 2²² = 26987148277 is a prime.

It is a super-2 number, since 2×26991342581² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (26991342583) 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, 1927953035 + ... + 1927953048.

It is an arithmetic number, because the mean of its divisors is an integer number (7711812168).

Almost surely, 2^26991342581 is an apocalyptic number.

It is an amenable number.

26991342581 is a deficient number, since it is larger than the sum of its proper divisors (3855906091).

26991342581 is an equidigital number, since it uses as much as digits as its factorization.

26991342581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3855906090.

The product of its digits is 933120, while the sum is 50.

The spelling of 26991342581 in words is "twenty-six billion, nine hundred ninety-one million, three hundred forty-two thousand, five hundred eighty-one".