18987749 has 4 divisors (see below), whose sum is σ = 20713920. Its totient is φ = 17261580.

The previous prime is 18987739. The next prime is 18987757. The reversal of 18987749 is 94778981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 94778981 = 11 ⋅8616271.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18987749 is a prime.

It is a super-2 number, since 2×18987749² = 721069224174002, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18987749.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18987739) 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 3 ways as a sum of consecutive naturals, for example, 863069 + ... + 863090.

It is an arithmetic number, because the mean of its divisors is an integer number (5178480).

Almost surely, 2^18987749 is an apocalyptic number.

It is an amenable number.

18987749 is a deficient number, since it is larger than the sum of its proper divisors (1726171).

18987749 is a wasteful number, since it uses less digits than its factorization.

18987749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1726170.

The product of its digits is 1016064, while the sum is 53.

The square root of 18987749 is about 4357.4934308614. The cubic root of 18987749 is about 266.7828006313.

The spelling of 18987749 in words is "eighteen million, nine hundred eighty-seven thousand, seven hundred forty-nine".