1771989607921 has 9 divisors (see below), whose sum is σ = 1918800385281. Its totient is φ = 1635666741072.

The previous prime is 1771989607909. The next prime is 1771989607931. The reversal of 1771989607921 is 1297069891771.

The square root of 1771989607921 is 1331161.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 190130009521 + 1581859598400 = 436039^2 + 1257720^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1771989607921 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1771989607901) 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 in 8 ways as a sum of consecutive naturals, for example, 17253895 + ... + 17356291.

It is an arithmetic number, because the mean of its divisors is an integer number (213200042809).

Almost surely, 2^{1771989607921} is an apocalyptic number.

1771989607921 is the 1331161-st square number.

1771989607921 is the 665581-st centered octagonal number.

It is an amenable number.

1771989607921 is a deficient number, since it is larger than the sum of its proper divisors (146810777360).

1771989607921 is an frugal number, since it uses more digits than its factorization.

1771989607921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204820 (or 102410 counting only the distinct ones).

The product of its (nonzero) digits is 24004512, while the sum is 67.

The spelling of 1771989607921 in words is "one trillion, seven hundred seventy-one billion, nine hundred eighty-nine million, six hundred seven thousand, nine hundred twenty-one".