866640 has 80 divisors (see below), whose sum is σ = 2821248. Its totient is φ = 219648.

The previous prime is 866639. The next prime is 866641. The reversal of 866640 is 46668.

866640 = 183² + 184² + ... + 205².

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (866639) and next prime (866641).

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 866598 and 866607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (866641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5442 + ... + 5598.

2⁸⁶⁶⁶⁴⁰ is an apocalyptic number.

866640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 866640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1410624).

866640 is an abundant number, since it is smaller than the sum of its proper divisors (1954608).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

866640 is a wasteful number, since it uses less digits than its factorization.

866640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 196 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 866640 is about 930.9350138436. The cubic root of 866640 is about 95.3409723233.

The spelling of 866640 in words is "eight hundred sixty-six thousand, six hundred forty".