1998136909 has 2 divisors, whose sum is σ = 1998136910. Its totient is φ = 1998136908.

The previous prime is 1998136901. The next prime is 1998136949. The reversal of 1998136909 is 9096318991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1996749225 + 1387684 = 44685^2 + 1178^2 .

It is a cyclic number.

It is not a de Polignac number, because 1998136909 - 2³ = 1998136901 is a prime.

It is a super-2 number, since 2×1998136909² = 7985102214216148562, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1998136909.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1998136901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999068454 + 999068455.

It is an arithmetic number, because the mean of its divisors is an integer number (999068455).

Almost surely, 2^1998136909 is an apocalyptic number.

It is an amenable number.

1998136909 is a deficient number, since it is larger than the sum of its proper divisors (1).

1998136909 is an equidigital number, since it uses as much as digits as its factorization.

1998136909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 944784, while the sum is 55.

The square root of 1998136909 is about 44700.5247060927. The cubic root of 1998136909 is about 1259.5297037560.

The spelling of 1998136909 in words is "one billion, nine hundred ninety-eight million, one hundred thirty-six thousand, nine hundred nine".