191989979478 has 144 divisors (see below), whose sum is σ = 485693874432. Its totient is φ = 54339012000.

The previous prime is 191989979477. The next prime is 191989979527. The reversal of 191989979478 is 874979989191.

It is a happy number.

It is a super-2 number, since 2×191989979478² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 191989979397 and 191989979406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191989979477) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 5056023 + ... + 5093853.

It is an arithmetic number, because the mean of its divisors is an integer number (3372874128).

Almost surely, 2^191989979478 is an apocalyptic number.

191989979478 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 191989979478, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (242846937216).

191989979478 is an abundant number, since it is smaller than the sum of its proper divisors (293703894954).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

191989979478 is a wasteful number, since it uses less digits than its factorization.

191989979478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37959 (or 37937 counting only the distinct ones).

The product of its digits is 740710656, while the sum is 81.

The spelling of 191989979478 in words is "one hundred ninety-one billion, nine hundred eighty-nine million, nine hundred seventy-nine thousand, four hundred seventy-eight".