18681840 has 180 divisors, whose sum is σ = 67230072. Its totient is φ = 4821120.

The previous prime is 18681833. The next prime is 18681851. The reversal of 18681840 is 4818681.

It is a tau number, because it is divible by the number of its divisors (180).

It is a super-2 number, since 2×18681840² = 698022291571200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

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 = 18681795 and 18681804.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 602625 + ... + 602655.

Almost surely, 2^18681840 is an apocalyptic number.

18681840 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 18681840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33615036).

18681840 is an abundant number, since it is smaller than the sum of its proper divisors (48548232).

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

18681840 is an equidigital number, since it uses as much as digits as its factorization.

18681840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90 (or 41 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 36.

The square root of 18681840 is about 4322.2494143675. The cubic root of 18681840 is about 265.3423367286.

The spelling of 18681840 in words is "eighteen million, six hundred eighty-one thousand, eight hundred forty".