91000018 has 4 divisors (see below), whose sum is σ = 136500030. Its totient is φ = 45500008.

The previous prime is 91000009. The next prime is 91000027. The reversal of 91000018 is 81000019.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81000019 = 17 ⋅4764707.

It is an interprime number because it is at equal distance from previous prime (91000009) and next prime (91000027).

It can be written as a sum of positive squares in only one way, i.e., 89624089 + 1375929 = 9467^2 + 1173^2 .

It is a junction number, because it is equal to n+sod(n) for n = 90999959 and 91000004.

It is an unprimeable number.

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, 22750003 + ... + 22750006.

Almost surely, 2^91000018 is an apocalyptic number.

91000018 is a deficient number, since it is larger than the sum of its proper divisors (45500012).

91000018 is a wasteful number, since it uses less digits than its factorization.

91000018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45500011.

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 91000018 is about 9539.3929576258. The cubic root of 91000018 is about 449.7941741843.

Subtracting from 91000018 its reverse (81000019), we obtain a palindrome (9999999).

The spelling of 91000018 in words is "ninety-one million, eighteen", and thus it is an aban number and an uban number.