18491917 has 2 divisors, whose sum is σ = 18491918. Its totient is φ = 18491916.

The previous prime is 18491911. The next prime is 18491927. The reversal of 18491917 is 71919481.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18139081 + 352836 = 4259^2 + 594^2 .

It is an emirp because it is prime and its reverse (71919481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18491917 - 2²³ = 10103309 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18491917.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18491911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9245958 + 9245959.

It is an arithmetic number, because the mean of its divisors is an integer number (9245959).

Almost surely, 2^18491917 is an apocalyptic number.

It is an amenable number.

18491917 is a deficient number, since it is larger than the sum of its proper divisors (1).

18491917 is an equidigital number, since it uses as much as digits as its factorization.

18491917 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 18491917 is about 4300.2229011994. Note that the first 3 decimals coincide. The cubic root of 18491917 is about 264.4400994521.

The spelling of 18491917 in words is "eighteen million, four hundred ninety-one thousand, nine hundred seventeen".