866638 has 4 divisors (see below), whose sum is σ = 1299960. Its totient is φ = 433318.

The previous prime is 866629. The next prime is 866639. The reversal of 866638 is 836668.

It is a semiprime because it is the product of two primes.

It is a super-2 number, since 2×866638² = 1502122846088, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 866597 and 866606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (866639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 216658 + ... + 216661.

It is an arithmetic number, because the mean of its divisors is an integer number (324990).

2⁸⁶⁶⁶³⁸ is an apocalyptic number.

866638 is a deficient number, since it is larger than the sum of its proper divisors (433322).

866638 is a wasteful number, since it uses less digits than its factorization.

866638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433321.

The product of its digits is 41472, while the sum is 37.

The square root of 866638 is about 930.9339396542. The cubic root of 866638 is about 95.3408989817.

It can be divided in two parts, 86 and 6638, that added together give a square (6724 = 82²).

The spelling of 866638 in words is "eight hundred sixty-six thousand, six hundred thirty-eight".