18656640 has 192 divisors, whose sum is σ = 66830400. Its totient is φ = 4792320.

The previous prime is 18656629. The next prime is 18656647. The reversal of 18656640 is 4665681.

18656640 is a `hidden beast` number, since 1 + 8 + 6 + 5 + 6 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 18656595 and 18656604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18656647) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 236121 + ... + 236199.

It is an arithmetic number, because the mean of its divisors is an integer number (348075).

Almost surely, 2^18656640 is an apocalyptic number.

18656640 is a gapful number since it is divisible by the number (10) 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 18656640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33415200).

18656640 is an abundant number, since it is smaller than the sum of its proper divisors (48173760).

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

18656640 is a wasteful number, since it uses less digits than its factorization.

18656640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The square root of 18656640 is about 4319.3332818851. Note that the first 3 decimals coincide. The cubic root of 18656640 is about 265.2229759719. Note that the first 3 decimals are identical.

The spelling of 18656640 in words is "eighteen million, six hundred fifty-six thousand, six hundred forty".