818640 has 80 divisors (see below), whose sum is σ = 2827200. Its totient is φ = 217728.

The previous prime is 818621. The next prime is 818659. The reversal of 818640 is 46818.

818640 = T₁₀ + T₁₁ + ... + T₁₆₉.

818640 is a `hidden beast` number, since 8 + 18 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (818621) and next prime (818659).

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 (27).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 818640.

It is an unprimeable number.

818640 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 (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1971 + ... + 2349.

It is an arithmetic number, because the mean of its divisors is an integer number (35340).

2⁸¹⁸⁶⁴⁰ is an apocalyptic number.

818640 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 818640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1413600).

818640 is an abundant number, since it is smaller than the sum of its proper divisors (2008560).

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

818640 is a wasteful number, since it uses less digits than its factorization.

818640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 401 (or 389 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 818640 is about 904.7872678149. The cubic root of 818640 is about 93.5472418000.

The spelling of 818640 in words is "eight hundred eighteen thousand, six hundred forty".