18406381 has 4 divisors (see below), whose sum is σ = 21035872. Its totient is φ = 15776892.

The previous prime is 18406379. The next prime is 18406471. The reversal of 18406381 is 18360481.

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: 18360481 = 167 ⋅109943.

It is a cyclic number.

It is not a de Polignac number, because 18406381 - 2¹ = 18406379 is a prime.

It is a super-2 number, since 2×18406381² = 677589723034322, 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 (18406321) 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, 1314735 + ... + 1314748.

It is an arithmetic number, because the mean of its divisors is an integer number (5258968).

Almost surely, 2^18406381 is an apocalyptic number.

It is an amenable number.

18406381 is a deficient number, since it is larger than the sum of its proper divisors (2629491).

18406381 is an equidigital number, since it uses as much as digits as its factorization.

18406381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2629490.

The product of its (nonzero) digits is 4608, while the sum is 31.

The square root of 18406381 is about 4290.2658425790. The cubic root of 18406381 is about 264.0317387997.

The spelling of 18406381 in words is "eighteen million, four hundred six thousand, three hundred eighty-one".