1998136409 has 2 divisors, whose sum is σ = 1998136410. Its totient is φ = 1998136408.

The previous prime is 1998136397. The next prime is 1998136417. The reversal of 1998136409 is 9046318991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1480710400 + 517426009 = 38480^2 + 22747^2 .

It is a cyclic number.

It is not a de Polignac number, because 1998136409 - 2²⁸ = 1729700953 is a prime.

It is not a weakly prime, because it can be changed into another prime (1998136909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999068204 + 999068205.

It is an arithmetic number, because the mean of its divisors is an integer number (999068205).

Almost surely, 2^1998136409 is an apocalyptic number.

It is an amenable number.

1998136409 is a deficient number, since it is larger than the sum of its proper divisors (1).

1998136409 is an equidigital number, since it uses as much as digits as its factorization.

1998136409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 419904, while the sum is 50.

The square root of 1998136409 is about 44700.5191133168. The cubic root of 1998136409 is about 1259.5295986973.

The spelling of 1998136409 in words is "one billion, nine hundred ninety-eight million, one hundred thirty-six thousand, four hundred nine".