266638 has 4 divisors (see below), whose sum is σ = 399960. Its totient is φ = 133318.

The previous prime is 266633. The next prime is 266641. The reversal of 266638 is 836662.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 836662 = 2 ⋅418331.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (266633) by changing a digit.

266638 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 66658 + ... + 66661.

It is an arithmetic number, because the mean of its divisors is an integer number (99990).

2²⁶⁶⁶³⁸ is an apocalyptic number.

266638 is a deficient number, since it is larger than the sum of its proper divisors (133322).

266638 is a wasteful number, since it uses less digits than its factorization.

266638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133321.

The product of its digits is 10368, while the sum is 31.

The square root of 266638 is about 516.3700223677. The cubic root of 266638 is about 64.3636524442.

It can be divided in two parts, 2666 and 38, that added together give a square (2704 = 52²).

The spelling of 266638 in words is "two hundred sixty-six thousand, six hundred thirty-eight".