1664686888681 has 2 divisors, whose sum is σ = 1664686888682. Its totient is φ = 1664686888680.

The previous prime is 1664686888673. The next prime is 1664686888741. The reversal of 1664686888681 is 1868886864661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 915581059600 + 749105829081 = 956860^2 + 865509^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664686888681 - 2³ = 1664686888673 is a prime.

It is a super-2 number, since 2×1664686888681² (a number of 25 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1664686888598 and 1664686888607.

It is not a weakly prime, because it can be changed into another prime (1664686889681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832343444340 + 832343444341.

It is an arithmetic number, because the mean of its divisors is an integer number (832343444341).

Almost surely, 2^{1664686888681} is an apocalyptic number.

It is an amenable number.

1664686888681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664686888681 is an equidigital number, since it uses as much as digits as its factorization.

1664686888681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1019215872, while the sum is 76.

The spelling of 1664686888681 in words is "one trillion, six hundred sixty-four billion, six hundred eighty-six million, eight hundred eighty-eight thousand, six hundred eighty-one".