18443991633961 has 4 divisors (see below), whose sum is σ = 18444018449232. Its totient is φ = 18443964818692.

The previous prime is 18443991633959. The next prime is 18443991634021. The reversal of 18443991633961 is 16933619934481.

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.

It is a cyclic number.

It is not a de Polignac number, because 18443991633961 - 2¹ = 18443991633959 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18443991633461) 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, 12347995 + ... + 13760848.

It is an arithmetic number, because the mean of its divisors is an integer number (4611004612308).

Almost surely, 2^{18443991633961} is an apocalyptic number.

It is an amenable number.

18443991633961 is a deficient number, since it is larger than the sum of its proper divisors (26815271).

18443991633961 is an equidigital number, since it uses as much as digits as its factorization.

18443991633961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26815270.

The product of its digits is 90699264, while the sum is 67.

The spelling of 18443991633961 in words is "eighteen trillion, four hundred forty-three billion, nine hundred ninety-one million, six hundred thirty-three thousand, nine hundred sixty-one".