1661899 has 2 divisors, whose sum is σ = 1661900. Its totient is φ = 1661898.

The previous prime is 1661893. The next prime is 1661917. The reversal of 1661899 is 9981661.

It is a weak prime.

It is an emirp because it is prime and its reverse (9981661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1661899 - 2¹¹ = 1659851 is a prime.

It is not a weakly prime, because it can be changed into another prime (1661893) 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 as a sum of consecutive naturals, namely, 830949 + 830950.

It is an arithmetic number, because the mean of its divisors is an integer number (830950).

2^1661899 is an apocalyptic number.

1661899 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661899 is an equidigital number, since it uses as much as digits as its factorization.

1661899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 40.

The square root of 1661899 is about 1289.1466169525. The cubic root of 1661899 is about 118.4499482998.

The spelling of 1661899 in words is "one million, six hundred sixty-one thousand, eight hundred ninety-nine".