18131551 has 2 divisors, whose sum is σ = 18131552. Its totient is φ = 18131550.

The previous prime is 18131507. The next prime is 18131557. The reversal of 18131551 is 15513181.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18131551 - 2⁹ = 18131039 is a prime.

It is equal to p_1159153 and since 18131551 and 1159153 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18131557) 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 as a sum of consecutive naturals, namely, 9065775 + 9065776.

It is an arithmetic number, because the mean of its divisors is an integer number (9065776).

Almost surely, 2^18131551 is an apocalyptic number.

18131551 is a deficient number, since it is larger than the sum of its proper divisors (1).

18131551 is an equidigital number, since it uses as much as digits as its factorization.

18131551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 600, while the sum is 25.

The square root of 18131551 is about 4258.1158979060. The cubic root of 18131551 is about 262.7110369429.

It can be divided in two parts, 1813 and 1551, that added together give a square (3364 = 58²).

The spelling of 18131551 in words is "eighteen million, one hundred thirty-one thousand, five hundred fifty-one".