266538721 has 4 divisors (see below), whose sum is σ = 266586372. Its totient is φ = 266491072.

The previous prime is 266538703. The next prime is 266538731. The reversal of 266538721 is 127835662.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127835662 = 2 ⋅63917831.

It can be written as a sum of positive squares in 2 ways, for example, as 58140625 + 208398096 = 7625^2 + 14436^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-266538721 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (266538731) 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, 14116 + ... + 27061.

It is an arithmetic number, because the mean of its divisors is an integer number (66646593).

Almost surely, 2^266538721 is an apocalyptic number.

It is an amenable number.

266538721 is a deficient number, since it is larger than the sum of its proper divisors (47651).

266538721 is an equidigital number, since it uses as much as digits as its factorization.

266538721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47650.

The product of its digits is 120960, while the sum is 40.

The square root of 266538721 is about 16326.0136285622. The cubic root of 266538721 is about 643.5566314499.

The spelling of 266538721 in words is "two hundred sixty-six million, five hundred thirty-eight thousand, seven hundred twenty-one".