18465991 has 2 divisors, whose sum is σ = 18465992. Its totient is φ = 18465990.

The previous prime is 18465989. The next prime is 18466001. The reversal of 18465991 is 19956481.

It is a weak prime.

It is an emirp because it is prime and its reverse (19956481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18465991 - 2¹ = 18465989 is a prime.

It is a super-2 number, since 2×18465991² = 681985647224162, which contains 22 as substring.

Together with 18465989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18465091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9232995 + 9232996.

It is an arithmetic number, because the mean of its divisors is an integer number (9232996).

Almost surely, 2^18465991 is an apocalyptic number.

18465991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18465991 is an equidigital number, since it uses as much as digits as its factorization.

18465991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 43.

The square root of 18465991 is about 4297.2073489651. The cubic root of 18465991 is about 264.3164583943.

It can be divided in two parts, 18 and 465991, that multiplied together give a palindrome (8387838).

The spelling of 18465991 in words is "eighteen million, four hundred sixty-five thousand, nine hundred ninety-one".