18991368 has 64 divisors (see below), whose sum is σ = 57556800. Its totient is φ = 5754240.

The previous prime is 18991361. The next prime is 18991373. The reversal of 18991368 is 86319981.

It is a super-2 number, since 2×18991368² = 721344117022848, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (18991361) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1621 + ... + 6372.

It is an arithmetic number, because the mean of its divisors is an integer number (899325).

Almost surely, 2^18991368 is an apocalyptic number.

18991368 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

18991368 is an abundant number, since it is smaller than the sum of its proper divisors (38565432).

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

18991368 is a wasteful number, since it uses less digits than its factorization.

18991368 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8019 (or 8009 counting only the distinct ones).

The product of its digits is 93312, while the sum is 45.

The square root of 18991368 is about 4357.9086727466. The cubic root of 18991368 is about 266.7997488510.

It can be divided in two parts, 189913 and 68, that added together give a palindrome (189981).

The spelling of 18991368 in words is "eighteen million, nine hundred ninety-one thousand, three hundred sixty-eight".