1645999 has 2 divisors, whose sum is σ = 1646000. Its totient is φ = 1645998.

The previous prime is 1645979. The next prime is 1646017. The reversal of 1645999 is 9995461.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1645999 - 2⁵ = 1645967 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1645909) 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, 822999 + 823000.

It is an arithmetic number, because the mean of its divisors is an integer number (823000).

2^1645999 is an apocalyptic number.

1645999 is a deficient number, since it is larger than the sum of its proper divisors (1).

1645999 is an equidigital number, since it uses as much as digits as its factorization.

1645999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 87480, while the sum is 43.

The square root of 1645999 is about 1282.9649254754. The cubic root of 1645999 is about 118.0709857284.

The spelling of 1645999 in words is "one million, six hundred forty-five thousand, nine hundred ninety-nine".