18131945 has 32 divisors (see below), whose sum is σ = 25310880. Its totient is φ = 12349440.

The previous prime is 18131941. The next prime is 18131951. The reversal of 18131945 is 54913181.

It can be written as a sum of positive squares in 16 ways, for example, as 14047504 + 4084441 = 3748^2 + 2021^2 .

It is not a de Polignac number, because 18131945 - 2² = 18131941 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18131941) 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 31 ways as a sum of consecutive naturals, for example, 67271 + ... + 67539.

It is an arithmetic number, because the mean of its divisors is an integer number (790965).

Almost surely, 2^18131945 is an apocalyptic number.

It is an amenable number.

18131945 is a deficient number, since it is larger than the sum of its proper divisors (7178935).

18131945 is a wasteful number, since it uses less digits than its factorization.

18131945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 365.

The product of its digits is 4320, while the sum is 32.

The square root of 18131945 is about 4258.1621622479. The cubic root of 18131945 is about 262.7129398395.

The spelling of 18131945 in words is "eighteen million, one hundred thirty-one thousand, nine hundred forty-five".