18121531 has 2 divisors, whose sum is σ = 18121532. Its totient is φ = 18121530.

The previous prime is 18121517. The next prime is 18121559. The reversal of 18121531 is 13512181.

It is a weak prime.

It is an emirp because it is prime and its reverse (13512181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18121531 - 2¹⁷ = 17990459 is a prime.

It is a super-2 number, since 2×18121531² = 656779771567922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18125531) 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 as a sum of consecutive naturals, namely, 9060765 + 9060766.

It is an arithmetic number, because the mean of its divisors is an integer number (9060766).

Almost surely, 2^18121531 is an apocalyptic number.

18121531 is a deficient number, since it is larger than the sum of its proper divisors (1).

18121531 is an equidigital number, since it uses as much as digits as its factorization.

18121531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 240, while the sum is 22.

The square root of 18121531 is about 4256.9391585974. The cubic root of 18121531 is about 262.6626342139.

It can be divided in two parts, 181 and 21531, that added together give a palindrome (21712).

The spelling of 18121531 in words is "eighteen million, one hundred twenty-one thousand, five hundred thirty-one".