18191819 has 16 divisors (see below), whose sum is σ = 19852128. Its totient is φ = 16607232.

The previous prime is 18191813. The next prime is 18191837. The reversal of 18191819 is 91819181.

18191819 = T₄₀ + T₄₁ + ... + T₄₇₇.

It is a de Polignac number, because none of the positive numbers 2^k-18191819 is a prime.

It is a super-2 number, since 2×18191819² = 661884557057522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18191813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 132719 + ... + 132855.

It is an arithmetic number, because the mean of its divisors is an integer number (1240758).

Almost surely, 2^18191819 is an apocalyptic number.

18191819 is a deficient number, since it is larger than the sum of its proper divisors (1660309).

18191819 is a wasteful number, since it uses less digits than its factorization.

18191819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 334.

The product of its digits is 5184, while the sum is 38.

The square root of 18191819 is about 4265.1868657774. The cubic root of 18191819 is about 263.0017926984.

The spelling of 18191819 in words is "eighteen million, one hundred ninety-one thousand, eight hundred nineteen".