19981791 has 6 divisors (see below), whose sum is σ = 28862600. Its totient is φ = 13321188.

The previous prime is 19981777. The next prime is 19981807. The reversal of 19981791 is 19718991.

It is not a de Polignac number, because 19981791 - 2⁶ = 19981727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19981891) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1110091 + ... + 1110108.

Almost surely, 2^19981791 is an apocalyptic number.

19981791 is a deficient number, since it is larger than the sum of its proper divisors (8880809).

19981791 is a wasteful number, since it uses less digits than its factorization.

19981791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2220205 (or 2220202 counting only the distinct ones).

The product of its digits is 40824, while the sum is 45.

The square root of 19981791 is about 4470.0996633185. The cubic root of 19981791 is about 271.3593585958.

The spelling of 19981791 in words is "nineteen million, nine hundred eighty-one thousand, seven hundred ninety-one".