87663991721 has 2 divisors, whose sum is σ = 87663991722. Its totient is φ = 87663991720.

The previous prime is 87663991717. The next prime is 87663991819. The reversal of 87663991721 is 12719936678.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 61374612121 + 26289379600 = 247739^2 + 162140^2 .

It is a cyclic number.

It is not a de Polignac number, because 87663991721 - 2² = 87663991717 is a prime.

It is not a weakly prime, because it can be changed into another prime (87663990721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43831995860 + 43831995861.

It is an arithmetic number, because the mean of its divisors is an integer number (43831995861).

Almost surely, 2^87663991721 is an apocalyptic number.

It is an amenable number.

87663991721 is a deficient number, since it is larger than the sum of its proper divisors (1).

87663991721 is an equidigital number, since it uses as much as digits as its factorization.

87663991721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6858432, while the sum is 59.

The spelling of 87663991721 in words is "eighty-seven billion, six hundred sixty-three million, nine hundred ninety-one thousand, seven hundred twenty-one".