266155991 has 4 divisors (see below), whose sum is σ = 266303184. Its totient is φ = 266008800.

The previous prime is 266155963. The next prime is 266156003. The reversal of 266155991 is 199551662.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199551662 = 2 ⋅99775831.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-266155991 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 (266155921) 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, 70850 + ... + 74511.

It is an arithmetic number, because the mean of its divisors is an integer number (66575796).

Almost surely, 2^266155991 is an apocalyptic number.

266155991 is a deficient number, since it is larger than the sum of its proper divisors (147193).

266155991 is a wasteful number, since it uses less digits than its factorization.

266155991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 147192.

The product of its digits is 145800, while the sum is 44.

The square root of 266155991 is about 16314.2879403301. The cubic root of 266155991 is about 643.2484505642.

The spelling of 266155991 in words is "two hundred sixty-six million, one hundred fifty-five thousand, nine hundred ninety-one".