1664889100981 has 2 divisors, whose sum is σ = 1664889100982. Its totient is φ = 1664889100980.

The previous prime is 1664889100939. The next prime is 1664889100991. The reversal of 1664889100981 is 1890019884661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1609777312900 + 55111788081 = 1268770^2 + 234759^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664889100981 - 2¹¹ = 1664889098933 is a prime.

It is a super-2 number, since 2×1664889100981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1664889100991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832444550490 + 832444550491.

It is an arithmetic number, because the mean of its divisors is an integer number (832444550491).

Almost surely, 2^{1664889100981} is an apocalyptic number.

It is an amenable number.

1664889100981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664889100981 is an equidigital number, since it uses as much as digits as its factorization.

1664889100981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5971968, while the sum is 61.

The spelling of 1664889100981 in words is "one trillion, six hundred sixty-four billion, eight hundred eighty-nine million, one hundred thousand, nine hundred eighty-one".