18987993 has 32 divisors (see below), whose sum is σ = 29366400. Its totient is φ = 12115008.

The previous prime is 18987977. The next prime is 18988003. The reversal of 18987993 is 39978981.

It is not a de Polignac number, because 18987993 - 2⁴ = 18987977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18887993) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 82803 + ... + 83031.

It is an arithmetic number, because the mean of its divisors is an integer number (917700).

Almost surely, 2^18987993 is an apocalyptic number.

It is an amenable number.

18987993 is a deficient number, since it is larger than the sum of its proper divisors (10378407).

18987993 is a wasteful number, since it uses less digits than its factorization.

18987993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358 (or 352 counting only the distinct ones).

The product of its digits is 979776, while the sum is 54.

The square root of 18987993 is about 4357.5214285187. The cubic root of 18987993 is about 266.7839433809.

The spelling of 18987993 in words is "eighteen million, nine hundred eighty-seven thousand, nine hundred ninety-three".