26691561 has 24 divisors (see below), whose sum is σ = 43709120. Its totient is φ = 15559776.

The previous prime is 26691551. The next prime is 26691563. The reversal of 26691561 is 16519662.

26691561 is a `hidden beast` number, since 2 + 6 + 6 + 91 + 561 = 666.

It is not a de Polignac number, because 26691561 - 2⁵ = 26691529 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (26691563) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3781 + ... + 8226.

Almost surely, 2^26691561 is an apocalyptic number.

It is an amenable number.

26691561 is a deficient number, since it is larger than the sum of its proper divisors (17017559).

26691561 is a wasteful number, since it uses less digits than its factorization.

26691561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12045 (or 12042 counting only the distinct ones).

The product of its digits is 19440, while the sum is 36.

The square root of 26691561 is about 5166.3876161202. The cubic root of 26691561 is about 298.8532555087.

The spelling of 26691561 in words is "twenty-six million, six hundred ninety-one thousand, five hundred sixty-one".