1621366664689 has 2 divisors, whose sum is σ = 1621366664690. Its totient is φ = 1621366664688.

The previous prime is 1621366664639. The next prime is 1621366664741. The reversal of 1621366664689 is 9864666631261.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1490389264225 + 130977400464 = 1220815^2 + 361908^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621366664689 - 2³⁵ = 1587006926321 is a prime.

It is a super-2 number, since 2×1621366664689² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1621366664689.

It is not a weakly prime, because it can be changed into another prime (1621366664639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810683332344 + 810683332345.

It is an arithmetic number, because the mean of its divisors is an integer number (810683332345).

Almost surely, 2^{1621366664689} is an apocalyptic number.

It is an amenable number.

1621366664689 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621366664689 is an equidigital number, since it uses as much as digits as its factorization.

1621366664689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80621568, while the sum is 64.

The spelling of 1621366664689 in words is "one trillion, six hundred twenty-one billion, three hundred sixty-six million, six hundred sixty-four thousand, six hundred eighty-nine".