1815664665181 has 4 divisors (see below), whose sum is σ = 1815976266112. Its totient is φ = 1815353064252.

The previous prime is 1815664665151. The next prime is 1815664665187.

1815664665181 is nontrivially palindromic in base 10.

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 1815664665181 - 2²⁹ = 1815127794269 is a prime.

It is a super-2 number, since 2×1815664665181² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1815664665187) 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, 155791725 + ... + 155803378.

It is an arithmetic number, because the mean of its divisors is an integer number (453994066528).

Almost surely, 2^{1815664665181} is an apocalyptic number.

It is an amenable number.

1815664665181 is a deficient number, since it is larger than the sum of its proper divisors (311600931).

1815664665181 is an equidigital number, since it uses as much as digits as its factorization.

1815664665181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311600930.

The product of its digits is 8294400, while the sum is 58.

The spelling of 1815664665181 in words is "one trillion, eight hundred fifteen billion, six hundred sixty-four million, six hundred sixty-five thousand, one hundred eighty-one".