18665971 has 4 divisors (see below), whose sum is σ = 18928944. Its totient is φ = 18403000.

The previous prime is 18665951. The next prime is 18665981. The reversal of 18665971 is 17956681.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17956681 = 71 ⋅252911.

It is a cyclic number.

It is not a de Polignac number, because 18665971 - 2⁹ = 18665459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18665921) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131380 + ... + 131521.

It is an arithmetic number, because the mean of its divisors is an integer number (4732236).

Almost surely, 2^18665971 is an apocalyptic number.

18665971 is a deficient number, since it is larger than the sum of its proper divisors (262973).

18665971 is an equidigital number, since it uses as much as digits as its factorization.

18665971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262972.

The product of its digits is 90720, while the sum is 43.

The square root of 18665971 is about 4320.4132904156. The cubic root of 18665971 is about 265.2671851314.

The spelling of 18665971 in words is "eighteen million, six hundred sixty-five thousand, nine hundred seventy-one".