99978161 has 2 divisors, whose sum is σ = 99978162. Its totient is φ = 99978160.

The previous prime is 99978121. The next prime is 99978187. The reversal of 99978161 is 16187999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 90250000 + 9728161 = 9500^2 + 3119^2 .

It is an emirp because it is prime and its reverse (16187999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 99978161 - 2⁶ = 99978097 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (99978101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49989080 + 49989081.

It is an arithmetic number, because the mean of its divisors is an integer number (49989081).

Almost surely, 2^99978161 is an apocalyptic number.

It is an amenable number.

99978161 is a deficient number, since it is larger than the sum of its proper divisors (1).

99978161 is an equidigital number, since it uses as much as digits as its factorization.

99978161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 50.

The square root of 99978161 is about 9998.9079903757. The cubic root of 99978161 is about 464.1250916817.

The spelling of 99978161 in words is "ninety-nine million, nine hundred seventy-eight thousand, one hundred sixty-one".