17995997824561 has 3 divisors (see below), whose sum is σ = 17996002066731. Its totient is φ = 17995993582392.

The previous prime is 17995997824537. The next prime is 17995997824643. The reversal of 17995997824561 is 16542879959971.

The square root of 17995997824561 is 4242169.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 13822639130161 + 4173358694400 = 3717881^2 + 2042880^2 .

It is not a de Polignac number, because 17995997824561 - 2⁷ = 17995997824433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (17995997824531) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2121085 + ... + 6363253.

It is an arithmetic number, because the mean of its divisors is an integer number (5998667355577).

Almost surely, 2^{17995997824561} is an apocalyptic number.

17995997824561 is the 4242169-th square number.

17995997824561 is the 2121085-th centered octagonal number.

It is an amenable number.

17995997824561 is a deficient number, since it is larger than the sum of its proper divisors (4242170).

17995997824561 is an frugal number, since it uses more digits than its factorization.

17995997824561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8484338 (or 4242169 counting only the distinct ones).

The product of its digits is 3086294400, while the sum is 82.

The spelling of 17995997824561 in words is "seventeen trillion, nine hundred ninety-five billion, nine hundred ninety-seven million, eight hundred twenty-four thousand, five hundred sixty-one".