18161819 has 4 divisors (see below), whose sum is σ = 19558896. Its totient is φ = 16764744.

The previous prime is 18161809. The next prime is 18161839. The reversal of 18161819 is 91816181.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18161819 - 2¹⁶ = 18096283 is a prime.

It is a super-2 number, since 2×18161819² = 659703338777522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18161809) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 698519 + ... + 698544.

It is an arithmetic number, because the mean of its divisors is an integer number (4889724).

Almost surely, 2^18161819 is an apocalyptic number.

18161819 is a deficient number, since it is larger than the sum of its proper divisors (1397077).

18161819 is a wasteful number, since it uses less digits than its factorization.

18161819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1397076.

The product of its digits is 3456, while the sum is 35.

The square root of 18161819 is about 4261.6685699383. The cubic root of 18161819 is about 262.8571416897.

The spelling of 18161819 in words is "eighteen million, one hundred sixty-one thousand, eight hundred nineteen".