1981993 has 4 divisors (see below), whose sum is σ = 2134468. Its totient is φ = 1829520.

The previous prime is 1981963. The next prime is 1981997. The reversal of 1981993 is 3991891.

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 1281424 + 700569 = 1132^2 + 837^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981993 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981997) 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, 76218 + ... + 76243.

It is an arithmetic number, because the mean of its divisors is an integer number (533617).

2^1981993 is an apocalyptic number.

1981993 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1981993 is a deficient number, since it is larger than the sum of its proper divisors (152475).

1981993 is a wasteful number, since it uses less digits than its factorization.

1981993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152474.

The product of its digits is 17496, while the sum is 40.

The square root of 1981993 is about 1407.8327315416. The cubic root of 1981993 is about 125.6128411621.

The spelling of 1981993 in words is "one million, nine hundred eighty-one thousand, nine hundred ninety-three".