1663643 has 4 divisors (see below), whose sum is σ = 1721040. Its totient is φ = 1606248.

The previous prime is 1663619. The next prime is 1663681. The reversal of 1663643 is 3463661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3463661 = 31 ⋅111731.

It is a cyclic number.

It is not a de Polignac number, because 1663643 - 2⁶ = 1663579 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 57367 = 1663643 / (1 + 6 + 6 + 3 + 6 + 4 + 3).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1663693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28655 + ... + 28712.

It is an arithmetic number, because the mean of its divisors is an integer number (430260).

2^1663643 is an apocalyptic number.

1663643 is a deficient number, since it is larger than the sum of its proper divisors (57397).

1663643 is an equidigital number, since it uses as much as digits as its factorization.

1663643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57396.

The product of its digits is 7776, while the sum is 29.

The square root of 1663643 is about 1289.8228560543. The cubic root of 1663643 is about 118.4913676823.

The spelling of 1663643 in words is "one million, six hundred sixty-three thousand, six hundred forty-three".