18123820121 has 4 divisors (see below), whose sum is σ = 19771440144. Its totient is φ = 16476200100.

The previous prime is 18123820103. The next prime is 18123820153. The reversal of 18123820121 is 12102832181.

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: 12102832181 = 11 ⋅1100257471.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18123820121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18123820321) 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, 823809995 + ... + 823810016.

It is an arithmetic number, because the mean of its divisors is an integer number (4942860036).

Almost surely, 2^18123820121 is an apocalyptic number.

18123820121 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18123820121 is a deficient number, since it is larger than the sum of its proper divisors (1647620023).

18123820121 is a wasteful number, since it uses less digits than its factorization.

18123820121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1647620022.

The product of its (nonzero) digits is 1536, while the sum is 29.

The spelling of 18123820121 in words is "eighteen billion, one hundred twenty-three million, eight hundred twenty thousand, one hundred twenty-one".