18991390 has 16 divisors (see below), whose sum is σ = 37292400. Its totient is φ = 6905920.

The previous prime is 18991373. The next prime is 18991403. The reversal of 18991390 is 9319981.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86215 + ... + 86434.

It is an arithmetic number, because the mean of its divisors is an integer number (2330775).

Almost surely, 2^18991390 is an apocalyptic number.

18991390 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

18991390 is a deficient number, since it is larger than the sum of its proper divisors (18301010).

18991390 is a wasteful number, since it uses less digits than its factorization.

18991390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172667.

The product of its (nonzero) digits is 17496, while the sum is 40.

The square root of 18991390 is about 4357.9111968924. The cubic root of 18991390 is about 266.7998518731.

The spelling of 18991390 in words is "eighteen million, nine hundred ninety-one thousand, three hundred ninety".