18991968 has 48 divisors (see below), whose sum is σ = 50175216. Its totient is φ = 6289920.

The previous prime is 18991949. The next prime is 18991969. The reversal of 18991968 is 86919981.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a self number, because there is not a number n which added to its sum of digits gives 18991968.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18991969) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16830 + ... + 17922.

It is an arithmetic number, because the mean of its divisors is an integer number (1045317).

Almost surely, 2^18991968 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18991968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25087608).

18991968 is an abundant number, since it is smaller than the sum of its proper divisors (31183248).

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

18991968 is a wasteful number, since it uses less digits than its factorization.

18991968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1287 (or 1279 counting only the distinct ones).

The product of its digits is 279936, while the sum is 51.

The square root of 18991968 is about 4357.9775125625. The cubic root of 18991968 is about 266.8025585163.

The spelling of 18991968 in words is "eighteen million, nine hundred ninety-one thousand, nine hundred sixty-eight".