1681993 has 4 divisors (see below), whose sum is σ = 1705108. Its totient is φ = 1658880.

The previous prime is 1681991. The next prime is 1682017. The reversal of 1681993 is 3991861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3991861 = 571 ⋅6991.

It can be written as a sum of positive squares in 2 ways, for example, as 627264 + 1054729 = 792^2 + 1027^2 .

It is a cyclic number.

It is not a de Polignac number, because 1681993 - 2¹ = 1681991 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (1681991) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11448 + ... + 11593.

It is an arithmetic number, because the mean of its divisors is an integer number (426277).

2^1681993 is an apocalyptic number.

It is an amenable number.

1681993 is a deficient number, since it is larger than the sum of its proper divisors (23115).

1681993 is an equidigital number, since it uses as much as digits as its factorization.

1681993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23114.

The product of its digits is 11664, while the sum is 37.

The square root of 1681993 is about 1296.9167282443. The cubic root of 1681993 is about 118.9254293533.

The spelling of 1681993 in words is "one million, six hundred eighty-one thousand, nine hundred ninety-three".