18491947 has 4 divisors (see below), whose sum is σ = 18502720. Its totient is φ = 18481176.

The previous prime is 18491939. The next prime is 18491951. The reversal of 18491947 is 74919481.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18491947 - 2³ = 18491939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18491917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2172 + ... + 6457.

It is an arithmetic number, because the mean of its divisors is an integer number (4625680).

Almost surely, 2^18491947 is an apocalyptic number.

18491947 is a deficient number, since it is larger than the sum of its proper divisors (10773).

18491947 is an equidigital number, since it uses as much as digits as its factorization.

18491947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10772.

The product of its digits is 72576, while the sum is 43.

The square root of 18491947 is about 4300.2263893893. The cubic root of 18491947 is about 264.4402424551.

It can be divided in two parts, 1 and 8491947, that added together give a palindrome (8491948).

The spelling of 18491947 in words is "eighteen million, four hundred ninety-one thousand, nine hundred forty-seven".