1990909 has 4 divisors (see below), whose sum is σ = 1996060. Its totient is φ = 1985760.

The previous prime is 1990907. The next prime is 1990927. The reversal of 1990909 is 9090991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 22500 + 1968409 = 150^2 + 1403^2 .

It is a cyclic number.

It is not a de Polignac number, because 1990909 - 2¹ = 1990907 is a prime.

It is a Duffinian number.

1990909 is a modest number, since divided by 909 gives 199 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1990907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1944 + ... + 2785.

It is an arithmetic number, because the mean of its divisors is an integer number (499015).

2^1990909 is an apocalyptic number.

It is an amenable number.

1990909 is a deficient number, since it is larger than the sum of its proper divisors (5151).

1990909 is an equidigital number, since it uses as much as digits as its factorization.

1990909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5150.

The product of its (nonzero) digits is 6561, while the sum is 37.

The square root of 1990909 is about 1410.9957476903. The cubic root of 1990909 is about 125.8009159752.

It can be divided in two parts, 19 and 90909, that multiplied together give a palindrome (1727271).

The spelling of 1990909 in words is "one million, nine hundred ninety thousand, nine hundred nine".