19998645517 has 8 divisors (see below), whose sum is σ = 20085748920. Its totient is φ = 19911655680.

The previous prime is 19998645461. The next prime is 19998645533. The reversal of 19998645517 is 71554689991.

It can be written as a sum of positive squares in 4 ways, for example, as 8484067881 + 11514577636 = 92109^2 + 107306^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19998645517 - 2¹⁹ = 19998121229 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 (19998645217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 334603 + ... + 389815.

It is an arithmetic number, because the mean of its divisors is an integer number (2510718615).

Almost surely, 2^19998645517 is an apocalyptic number.

It is an amenable number.

19998645517 is a deficient number, since it is larger than the sum of its proper divisors (87103403).

19998645517 is a wasteful number, since it uses less digits than its factorization.

19998645517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56783.

The product of its digits is 24494400, while the sum is 64.

The spelling of 19998645517 in words is "nineteen billion, nine hundred ninety-eight million, six hundred forty-five thousand, five hundred seventeen".