18211954991 has 16 divisors (see below), whose sum is σ = 18838659840. Its totient is φ = 17594902080.

The previous prime is 18211954987. The next prime is 18211955081. The reversal of 18211954991 is 19945911281.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 18211954991 - 2² = 18211954987 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 (18211954391) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4830155 + ... + 4833923.

It is an arithmetic number, because the mean of its divisors is an integer number (1177416240).

Almost surely, 2^18211954991 is an apocalyptic number.

18211954991 is a deficient number, since it is larger than the sum of its proper divisors (626704849).

18211954991 is a wasteful number, since it uses less digits than its factorization.

18211954991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5006.

The product of its digits is 233280, while the sum is 50.

The spelling of 18211954991 in words is "eighteen billion, two hundred eleven million, nine hundred fifty-four thousand, nine hundred ninety-one".