18219791 has 2 divisors, whose sum is σ = 18219792. Its totient is φ = 18219790.

The previous prime is 18219787. The next prime is 18219793. The reversal of 18219791 is 19791281.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18219791 - 2² = 18219787 is a prime.

It is a Sophie Germain prime.

Together with 18219793, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18219793) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9109895 + 9109896.

It is an arithmetic number, because the mean of its divisors is an integer number (9109896).

Almost surely, 2^18219791 is an apocalyptic number.

18219791 is a deficient number, since it is larger than the sum of its proper divisors (1).

18219791 is an equidigital number, since it uses as much as digits as its factorization.

18219791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 38.

The square root of 18219791 is about 4268.4647122824. The cubic root of 18219791 is about 263.1365221021.

The spelling of 18219791 in words is "eighteen million, two hundred nineteen thousand, seven hundred ninety-one".