19661230513991 has 4 divisors (see below), whose sum is σ = 21448615106184. Its totient is φ = 17873845921800.

The previous prime is 19661230513949. The next prime is 19661230514047. The reversal of 19661230513991 is 19931503216691.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 19661230513991 - 2⁶ = 19661230513927 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 (19661230513291) 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, 893692296080 + ... + 893692296101.

It is an arithmetic number, because the mean of its divisors is an integer number (5362153776546).

Almost surely, 2^{19661230513991} is an apocalyptic number.

19661230513991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

19661230513991 is a deficient number, since it is larger than the sum of its proper divisors (1787384592193).

19661230513991 is a wasteful number, since it uses less digits than its factorization.

19661230513991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1787384592192.

The product of its (nonzero) digits is 2361960, while the sum is 56.

The spelling of 19661230513991 in words is "nineteen trillion, six hundred sixty-one billion, two hundred thirty million, five hundred thirteen thousand, nine hundred ninety-one".