3885664921681 has 3 divisors (see below), whose sum is σ = 3885666892891. Its totient is φ = 3885662950472.

The previous prime is 3885664921679. The next prime is 3885664921687. The reversal of 3885664921681 is 1861294665883.

The square root of 3885664921681 is 1971209.

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., 3732658776081 + 153006145600 = 1932009^2 + 391160^2 .

It is not a de Polignac number, because 3885664921681 - 2¹ = 3885664921679 is a prime.

It is a super-2 number, since 2×3885664921681² (a number of 26 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3885664921687) 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, 985605 + ... + 2956813.

Almost surely, 2^{3885664921681} is an apocalyptic number.

3885664921681 is the 1971209-th square number.

3885664921681 is the 985605-th centered octagonal number.

It is an amenable number.

3885664921681 is a deficient number, since it is larger than the sum of its proper divisors (1971210).

3885664921681 is an frugal number, since it uses more digits than its factorization.

3885664921681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3942418 (or 1971209 counting only the distinct ones).

The product of its digits is 119439360, while the sum is 67.

The spelling of 3885664921681 in words is "three trillion, eight hundred eighty-five billion, six hundred sixty-four million, nine hundred twenty-one thousand, six hundred eighty-one".