999887772661 has 2 divisors, whose sum is σ = 999887772662. Its totient is φ = 999887772660.

The previous prime is 999887772647. The next prime is 999887772707. The reversal of 999887772661 is 166277788999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 776566312900 + 223321459761 = 881230^2 + 472569^2 .

It is a cyclic number.

It is not a de Polignac number, because 999887772661 - 2¹⁷ = 999887641589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999887772641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499943886330 + 499943886331.

It is an arithmetic number, because the mean of its divisors is an integer number (499943886331).

Almost surely, 2^999887772661 is an apocalyptic number.

999887772661 is the 447189-th centered decagonal number.

It is an amenable number.

999887772661 is a deficient number, since it is larger than the sum of its proper divisors (1).

999887772661 is an equidigital number, since it uses as much as digits as its factorization.

999887772661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1152216576, while the sum is 79.

The spelling of 999887772661 in words is "nine hundred ninety-nine billion, eight hundred eighty-seven million, seven hundred seventy-two thousand, six hundred sixty-one".