1989237544661 has 2 divisors, whose sum is σ = 1989237544662. Its totient is φ = 1989237544660.

The previous prime is 1989237544649. The next prime is 1989237544699. The reversal of 1989237544661 is 1664457329891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1985052748561 + 4184796100 = 1408919^2 + 64690^2 .

It is an emirp because it is prime and its reverse (1664457329891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1989237544661 - 2³⁴ = 1972057675477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1989237544561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 994618772330 + 994618772331.

It is an arithmetic number, because the mean of its divisors is an integer number (994618772331).

Almost surely, 2^{1989237544661} is an apocalyptic number.

It is an amenable number.

1989237544661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1989237544661 is an equidigital number, since it uses as much as digits as its factorization.

1989237544661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 78382080, while the sum is 65.

The spelling of 1989237544661 in words is "one trillion, nine hundred eighty-nine billion, two hundred thirty-seven million, five hundred forty-four thousand, six hundred sixty-one".