18131506 has 4 divisors (see below), whose sum is σ = 27197262. Its totient is φ = 9065752.

The previous prime is 18131501. The next prime is 18131507. The reversal of 18131506 is 60513181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 60513181 = 1787 ⋅33863.

It can be written as a sum of positive squares in only one way, i.e., 9865881 + 8265625 = 3141^2 + 2875^2 .

It is not an unprimeable number, because it can be changed into a prime (18131501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4532875 + ... + 4532878.

Almost surely, 2^18131506 is an apocalyptic number.

18131506 is a deficient number, since it is larger than the sum of its proper divisors (9065756).

18131506 is an equidigital number, since it uses as much as digits as its factorization.

18131506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9065755.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 18131506 is about 4258.1106138756. The cubic root of 18131506 is about 262.7108196052.

Adding to 18131506 its reverse (60513181), we get a palindrome (78644687).

The spelling of 18131506 in words is "eighteen million, one hundred thirty-one thousand, five hundred six".