18197991 has 48 divisors (see below), whose sum is σ = 33047040. Its totient is φ = 9408960.

The previous prime is 18197941. The next prime is 18198001. The reversal of 18197991 is 19979181.

It is not a de Polignac number, because 18197991 - 2⁷ = 18197863 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18197911) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 27201 + ... + 27861.

It is an arithmetic number, because the mean of its divisors is an integer number (688480).

Almost surely, 2^18197991 is an apocalyptic number.

18197991 is a deficient number, since it is larger than the sum of its proper divisors (14849049).

18197991 is a wasteful number, since it uses less digits than its factorization.

18197991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 716 (or 713 counting only the distinct ones).

The product of its digits is 40824, while the sum is 45.

The square root of 18197991 is about 4265.9103366105. The cubic root of 18197991 is about 263.0315325048.

The spelling of 18197991 in words is "eighteen million, one hundred ninety-seven thousand, nine hundred ninety-one".