989878661 has 2 divisors, whose sum is σ = 989878662. Its totient is φ = 989878660.

The previous prime is 989878651. The next prime is 989878693. The reversal of 989878661 is 166878989.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 989102500 + 776161 = 31450^2 + 881^2 .

It is a cyclic number.

It is not a de Polignac number, because 989878661 - 2¹⁴ = 989862277 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 989878594 and 989878603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (989878651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 494939330 + 494939331.

It is an arithmetic number, because the mean of its divisors is an integer number (494939331).

Almost surely, 2^989878661 is an apocalyptic number.

It is an amenable number.

989878661 is a deficient number, since it is larger than the sum of its proper divisors (1).

989878661 is an equidigital number, since it uses as much as digits as its factorization.

989878661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10450944, while the sum is 62.

The square root of 989878661 is about 31462.3371827333. The cubic root of 989878661 is about 996.6147735062.

The spelling of 989878661 in words is "nine hundred eighty-nine million, eight hundred seventy-eight thousand, six hundred sixty-one".