18921387 has 8 divisors (see below), whose sum is σ = 26325504. Its totient is φ = 12065768.

The previous prime is 18921379. The next prime is 18921431. The reversal of 18921387 is 78312981.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18921387 - 2³ = 18921379 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18921317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 137043 + ... + 137180.

It is an arithmetic number, because the mean of its divisors is an integer number (3290688).

Almost surely, 2^18921387 is an apocalyptic number.

18921387 is a deficient number, since it is larger than the sum of its proper divisors (7404117).

18921387 is a wasteful number, since it uses less digits than its factorization.

18921387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 274249.

The product of its digits is 24192, while the sum is 39.

The square root of 18921387 is about 4349.8720670843. The cubic root of 18921387 is about 266.4716367375.

The spelling of 18921387 in words is "eighteen million, nine hundred twenty-one thousand, three hundred eighty-seven".