19711991 has 6 divisors (see below), whose sum is σ = 21345120. Its totient is φ = 18195528.

The previous prime is 19711973. The next prime is 19712039. The reversal of 19711991 is 19911791.

It is not a de Polignac number, because 19711991 - 2⁶ = 19711927 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 (19711921) 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, 58151 + ... + 58488.

It is an arithmetic number, because the mean of its divisors is an integer number (3557520).

Almost surely, 2^19711991 is an apocalyptic number.

19711991 is a deficient number, since it is larger than the sum of its proper divisors (1633129).

19711991 is a wasteful number, since it uses less digits than its factorization.

19711991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116665 (or 116652 counting only the distinct ones).

The product of its digits is 5103, while the sum is 38.

The square root of 19711991 is about 4439.8188026090. The cubic root of 19711991 is about 270.1324955559.

It can be divided in two parts, 19711 and 991, that added together give a palindrome (20702).

The spelling of 19711991 in words is "nineteen million, seven hundred eleven thousand, nine hundred ninety-one".