18421638 has 8 divisors (see below), whose sum is σ = 36843288. Its totient is φ = 6140544.

The previous prime is 18421633. The next prime is 18421639. The reversal of 18421638 is 83612481.

It is a sphenic number, since it is the product of 3 distinct primes.

18421638 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 18421599 and 18421608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18421631) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 1535131 + ... + 1535142.

It is an arithmetic number, because the mean of its divisors is an integer number (4605411).

Almost surely, 2^18421638 is an apocalyptic number.

18421638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

18421638 is a wasteful number, since it uses less digits than its factorization.

18421638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3070278.

The product of its digits is 9216, while the sum is 33.

The square root of 18421638 is about 4292.0435692104. The cubic root of 18421638 is about 264.1046703866.

It can be divided in two parts, 1842 and 1638, that multiplied together give a triangular number (3017196 = T₂₄₅₆).

The spelling of 18421638 in words is "eighteen million, four hundred twenty-one thousand, six hundred thirty-eight".