18001997 has 8 divisors (see below), whose sum is σ = 20527416. Its totient is φ = 15639552.

The previous prime is 18001981. The next prime is 18001999. The reversal of 18001997 is 79910081.

It can be written as a sum of positive squares in 4 ways, for example, as 454276 + 17547721 = 674^2 + 4189^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18001997 - 2⁴ = 18001981 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18001999) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40508 + ... + 40949.

It is an arithmetic number, because the mean of its divisors is an integer number (2565927).

Almost surely, 2^18001997 is an apocalyptic number.

18001997 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

It is an amenable number.

18001997 is a deficient number, since it is larger than the sum of its proper divisors (2525419).

18001997 is a wasteful number, since it uses less digits than its factorization.

18001997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81487.

The product of its (nonzero) digits is 4536, while the sum is 35.

The square root of 18001997 is about 4242.8760292990. The cubic root of 18001997 is about 262.0838309524.

The spelling of 18001997 in words is "eighteen million, one thousand, nine hundred ninety-seven".