99780405688891 has 2 divisors, whose sum is σ = 99780405688892. Its totient is φ = 99780405688890.

The previous prime is 99780405688793. The next prime is 99780405688967. The reversal of 99780405688891 is 19888650408799.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 99780405688891 - 2⁷ = 99780405688763 is a prime.

It is a super-2 number, since 2×99780405688891² (a number of 29 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (99780405682891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49890202844445 + 49890202844446.

It is an arithmetic number, because the mean of its divisors is an integer number (49890202844446).

Almost surely, 2^{99780405688891} is an apocalyptic number.

99780405688891 is a deficient number, since it is larger than the sum of its proper divisors (1).

99780405688891 is an equidigital number, since it uses as much as digits as its factorization.

99780405688891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2508226560, while the sum is 82.

The spelling of 99780405688891 in words is "ninety-nine trillion, seven hundred eighty billion, four hundred five million, six hundred eighty-eight thousand, eight hundred ninety-one".