18628381 has 4 divisors (see below), whose sum is σ = 18637632. Its totient is φ = 18619132.

The previous prime is 18628373. The next prime is 18628397. The reversal of 18628381 is 18382681.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18628381 - 2³ = 18628373 is a prime.

It is a super-2 number, since 2×18628381² = 694033157362322, 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 18628381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18628361) 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, 181 + ... + 6106.

It is an arithmetic number, because the mean of its divisors is an integer number (4659408).

Almost surely, 2^18628381 is an apocalyptic number.

It is an amenable number.

18628381 is a deficient number, since it is larger than the sum of its proper divisors (9251).

18628381 is an equidigital number, since it uses as much as digits as its factorization.

18628381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9250.

The product of its digits is 18432, while the sum is 37.

The square root of 18628381 is about 4316.0608197754. The cubic root of 18628381 is about 265.0889982312.

The spelling of 18628381 in words is "eighteen million, six hundred twenty-eight thousand, three hundred eighty-one".