18921487 has 4 divisors (see below), whose sum is σ = 20377000. Its totient is φ = 17465976.

The previous prime is 18921457. The next prime is 18921503. The reversal of 18921487 is 78412981.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18921487 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18921457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 727737 + ... + 727762.

It is an arithmetic number, because the mean of its divisors is an integer number (5094250).

Almost surely, 2^18921487 is an apocalyptic number.

18921487 is a deficient number, since it is larger than the sum of its proper divisors (1455513).

18921487 is a wasteful number, since it uses less digits than its factorization.

18921487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1455512.

The product of its digits is 32256, while the sum is 40.

The square root of 18921487 is about 4349.8835616600. The cubic root of 18921487 is about 266.4721061731.

The spelling of 18921487 in words is "eighteen million, nine hundred twenty-one thousand, four hundred eighty-seven".