1664542445021 has 2 divisors, whose sum is σ = 1664542445022. Its totient is φ = 1664542445020.

The previous prime is 1664542444991. The next prime is 1664542445047. The reversal of 1664542445021 is 1205442454661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1594840636900 + 69701808121 = 1262870^2 + 264011^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1664542445021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1664542445821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832271222510 + 832271222511.

It is an arithmetic number, because the mean of its divisors is an integer number (832271222511).

Almost surely, 2^{1664542445021} is an apocalyptic number.

It is an amenable number.

1664542445021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664542445021 is an equidigital number, since it uses as much as digits as its factorization.

1664542445021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 921600, while the sum is 44.

Adding to 1664542445021 its reverse (1205442454661), we get a palindrome (2869984899682).

The spelling of 1664542445021 in words is "one trillion, six hundred sixty-four billion, five hundred forty-two million, four hundred forty-five thousand, twenty-one".