9999888886661 has 2 divisors, whose sum is σ = 9999888886662. Its totient is φ = 9999888886660.

The previous prime is 9999888886643. The next prime is 9999888886667. The reversal of 9999888886661 is 1666888889999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9601972677025 + 397916209636 = 3098705^2 + 630806^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9999888886661 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9999888886667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4999944443330 + 4999944443331.

It is an arithmetic number, because the mean of its divisors is an integer number (4999944443331).

Almost surely, 2^{9999888886661} is an apocalyptic number.

It is an amenable number.

9999888886661 is a deficient number, since it is larger than the sum of its proper divisors (1).

9999888886661 is an equidigital number, since it uses as much as digits as its factorization.

9999888886661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46438023168, while the sum is 95.

The spelling of 9999888886661 in words is "nine trillion, nine hundred ninety-nine billion, eight hundred eighty-eight million, eight hundred eighty-six thousand, six hundred sixty-one".