18643406261 has 4 divisors (see below), whose sum is σ = 18725536032. Its totient is φ = 18561276492.

The previous prime is 18643406213. The next prime is 18643406311. The reversal of 18643406261 is 16260434681.

It is a happy number.

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: 16260434681 = 31 ⋅524530151.

It is a cyclic number.

It is not a de Polignac number, because 18643406261 - 2²² = 18639211957 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 (18643408261) 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, 41064545 + ... + 41064998.

It is an arithmetic number, because the mean of its divisors is an integer number (4681384008).

Almost surely, 2^18643406261 is an apocalyptic number.

It is an amenable number.

18643406261 is a deficient number, since it is larger than the sum of its proper divisors (82129771).

18643406261 is an equidigital number, since it uses as much as digits as its factorization.

18643406261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82129770.

The product of its (nonzero) digits is 165888, while the sum is 41.

The spelling of 18643406261 in words is "eighteen billion, six hundred forty-three million, four hundred six thousand, two hundred sixty-one".