18981381 has 4 divisors (see below), whose sum is σ = 25308512. Its totient is φ = 12654252.

The previous prime is 18981377. The next prime is 18981427. The reversal of 18981381 is 18318981.

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.

It is not a de Polignac number, because 18981381 - 2² = 18981377 is a prime.

It is a super-2 number, since 2×18981381² = 720585649334322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18981881) 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, 3163561 + ... + 3163566.

It is an arithmetic number, because the mean of its divisors is an integer number (6327128).

Almost surely, 2^18981381 is an apocalyptic number.

It is an amenable number.

18981381 is a deficient number, since it is larger than the sum of its proper divisors (6327131).

18981381 is an equidigital number, since it uses as much as digits as its factorization.

18981381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6327130.

The product of its digits is 13824, while the sum is 39.

The square root of 18981381 is about 4356.7626742801. The cubic root of 18981381 is about 266.7529732791.

The spelling of 18981381 in words is "eighteen million, nine hundred eighty-one thousand, three hundred eighty-one".