18491791 has 2 divisors, whose sum is σ = 18491792. Its totient is φ = 18491790.

The previous prime is 18491777. The next prime is 18491813. The reversal of 18491791 is 19719481.

It is a weak prime.

It is an emirp because it is prime and its reverse (19719481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18491791 - 2¹¹ = 18489743 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18491771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9245895 + 9245896.

It is an arithmetic number, because the mean of its divisors is an integer number (9245896).

Almost surely, 2^18491791 is an apocalyptic number.

18491791 is a deficient number, since it is larger than the sum of its proper divisors (1).

18491791 is an equidigital number, since it uses as much as digits as its factorization.

18491791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 40.

The square root of 18491791 is about 4300.2082507711. The cubic root of 18491791 is about 264.4394988378.

The spelling of 18491791 in words is "eighteen million, four hundred ninety-one thousand, seven hundred ninety-one".