18661840 has 40 divisors (see below), whose sum is σ = 43568640. Its totient is φ = 7433856.

The previous prime is 18661831. The next prime is 18661843. The reversal of 18661840 is 4816681.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 18661796 and 18661805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18661843) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38077 + ... + 38563.

It is an arithmetic number, because the mean of its divisors is an integer number (1089216).

Almost surely, 2^18661840 is an apocalyptic number.

18661840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18661840 is an abundant number, since it is smaller than the sum of its proper divisors (24906800).

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

18661840 is a wasteful number, since it uses less digits than its factorization.

18661840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 979 (or 973 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 18661840 is about 4319.9351846990. The cubic root of 18661840 is about 265.2476147665.

It can be divided in two parts, 186 and 61840, that added together give a palindrome (62026).

The spelling of 18661840 in words is "eighteen million, six hundred sixty-one thousand, eight hundred forty".