1663818791881 has 27 divisors (see below), whose sum is σ = 1819413925173. Its totient is φ = 1521245849760.

The previous prime is 1663818791867. The next prime is 1663818791927. The reversal of 1663818791881 is 1881978183661.

The square root of 1663818791881 is 1289891.

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

It can be written as a sum of positive squares in 4 ways, for example, as 52950151881 + 1610868640000 = 230109^2 + 1269200^2 .

It is not a de Polignac number, because 1663818791881 - 2³⁵ = 1629459053513 is a prime.

It is a super-2 number, since 2×1663818791881² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1663818791801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 710728771 + ... + 710731111.

Almost surely, 2^{1663818791881} is an apocalyptic number.

1663818791881 is the 1289891-st square number.

1663818791881 is the 644946-th centered octagonal number.

It is an amenable number.

1663818791881 is a deficient number, since it is larger than the sum of its proper divisors (155595133292).

1663818791881 is an frugal number, since it uses more digits than its factorization.

1663818791881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4778 (or 2389 counting only the distinct ones).

The product of its digits is 27869184, while the sum is 67.

The spelling of 1663818791881 in words is "one trillion, six hundred sixty-three billion, eight hundred eighteen million, seven hundred ninety-one thousand, eight hundred eighty-one".