18471991 has 8 divisors (see below), whose sum is σ = 19162944. Its totient is φ = 17791200.

The previous prime is 18471953. The next prime is 18472031. The reversal of 18471991 is 19917481.

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 18471991 - 2⁷ = 18471863 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18471091) 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, 1266 + ... + 6208.

It is an arithmetic number, because the mean of its divisors is an integer number (2395368).

Almost surely, 2^18471991 is an apocalyptic number.

18471991 is a deficient number, since it is larger than the sum of its proper divisors (690953).

18471991 is a wasteful number, since it uses less digits than its factorization.

18471991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5081.

The product of its digits is 18144, while the sum is 40.

The square root of 18471991 is about 4297.9054200855. The cubic root of 18471991 is about 264.3450826730.

The spelling of 18471991 in words is "eighteen million, four hundred seventy-one thousand, nine hundred ninety-one".