18723981 has 8 divisors (see below), whose sum is σ = 25003360. Its totient is φ = 12463632.

The previous prime is 18723979. The next prime is 18723983. The reversal of 18723981 is 18932781.

It is an interprime number because it is at equal distance from previous prime (18723979) and next prime (18723983).

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

It is not a de Polignac number, because 18723981 - 2¹ = 18723979 is a prime.

It is a super-2 number, since 2×18723981² = 701174928976722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18723983) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 2275 + ... + 6528.

It is an arithmetic number, because the mean of its divisors is an integer number (3125420).

Almost surely, 2^18723981 is an apocalyptic number.

It is an amenable number.

18723981 is a deficient number, since it is larger than the sum of its proper divisors (6279379).

18723981 is an equidigital number, since it uses as much as digits as its factorization.

18723981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9515.

The product of its digits is 24192, while the sum is 39.

The square root of 18723981 is about 4327.1215605758. The cubic root of 18723981 is about 265.5416995728.

The spelling of 18723981 in words is "eighteen million, seven hundred twenty-three thousand, nine hundred eighty-one".