26991561 has 16 divisors (see below), whose sum is σ = 36590400. Its totient is φ = 17696448.

The previous prime is 26991557. The next prime is 26991577. The reversal of 26991561 is 16519962.

It is not a de Polignac number, because 26991561 - 2² = 26991557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (26991521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 64210 + ... + 64628.

It is an arithmetic number, because the mean of its divisors is an integer number (2286900).

Almost surely, 2^26991561 is an apocalyptic number.

It is an amenable number.

26991561 is a deficient number, since it is larger than the sum of its proper divisors (9598839).

26991561 is a wasteful number, since it uses less digits than its factorization.

26991561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728.

The product of its digits is 29160, while the sum is 39.

The square root of 26991561 is about 5195.3403160909. The cubic root of 26991561 is about 299.9687411875.

The spelling of 26991561 in words is "twenty-six million, nine hundred ninety-one thousand, five hundred sixty-one".