99911921 has 2 divisors, whose sum is σ = 99911922. Its totient is φ = 99911920.

The previous prime is 99911897. The next prime is 99911923. The reversal of 99911921 is 12911999.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54538225 + 45373696 = 7385^2 + 6736^2 .

It is an emirp because it is prime and its reverse (12911999) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-99911921 is a prime.

It is a Sophie Germain prime.

Together with 99911923, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (99911923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49955960 + 49955961.

It is an arithmetic number, because the mean of its divisors is an integer number (49955961).

Almost surely, 2^99911921 is an apocalyptic number.

It is an amenable number.

99911921 is a deficient number, since it is larger than the sum of its proper divisors (1).

99911921 is an equidigital number, since it uses as much as digits as its factorization.

99911921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13122, while the sum is 41.

The square root of 99911921 is about 9995.5950798339. The cubic root of 99911921 is about 464.0225678307.

The spelling of 99911921 in words is "ninety-nine million, nine hundred eleven thousand, nine hundred twenty-one".