99991609 has 2 divisors, whose sum is σ = 99991610. Its totient is φ = 99991608.

The previous prime is 99991583. The next prime is 99991667. The reversal of 99991609 is 90619999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69222400 + 30769209 = 8320^2 + 5547^2 .

It is a cyclic number.

It is not a de Polignac number, because 99991609 - 2⁷ = 99991481 is a prime.

It is not a weakly prime, because it can be changed into another prime (99991009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49995804 + 49995805.

It is an arithmetic number, because the mean of its divisors is an integer number (49995805).

Almost surely, 2^99991609 is an apocalyptic number.

It is an amenable number.

99991609 is a deficient number, since it is larger than the sum of its proper divisors (1).

99991609 is an equidigital number, since it uses as much as digits as its factorization.

99991609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 354294, while the sum is 52.

The square root of 99991609 is about 9999.5804411985. The cubic root of 99991609 is about 464.1459004742.

The spelling of 99991609 in words is "ninety-nine million, nine hundred ninety-one thousand, six hundred nine".