18021681109 has 4 divisors (see below), whose sum is σ = 18440790016. Its totient is φ = 17602572204.

The previous prime is 18021681061. The next prime is 18021681133. The reversal of 18021681109 is 90118612081.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90118612081 = 421 ⋅214058461.

It is a cyclic number.

It is not a de Polignac number, because 18021681109 - 2¹⁷ = 18021550037 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 (18021681169) 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, 209554389 + ... + 209554474.

It is an arithmetic number, because the mean of its divisors is an integer number (4610197504).

Almost surely, 2^18021681109 is an apocalyptic number.

It is an amenable number.

18021681109 is a deficient number, since it is larger than the sum of its proper divisors (419108907).

18021681109 is an equidigital number, since it uses as much as digits as its factorization.

18021681109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 419108906.

The product of its (nonzero) digits is 6912, while the sum is 37.

The spelling of 18021681109 in words is "eighteen billion, twenty-one million, six hundred eighty-one thousand, one hundred nine".