18365981 has 4 divisors (see below), whose sum is σ = 18958464. Its totient is φ = 17773500.

The previous prime is 18365969. The next prime is 18365993. The reversal of 18365981 is 18956381.

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: 18956381 = 557 ⋅34033.

It is an interprime number because it is at equal distance from previous prime (18365969) and next prime (18365993).

It is a cyclic number.

It is not a de Polignac number, because 18365981 - 2⁶ = 18365917 is a prime.

It is a super-2 number, since 2×18365981² = 674618516184722, 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 (18365911) 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, 296195 + ... + 296256.

It is an arithmetic number, because the mean of its divisors is an integer number (4739616).

Almost surely, 2^18365981 is an apocalyptic number.

It is an amenable number.

18365981 is a deficient number, since it is larger than the sum of its proper divisors (592483).

18365981 is an equidigital number, since it uses as much as digits as its factorization.

18365981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592482.

The product of its digits is 51840, while the sum is 41.

The square root of 18365981 is about 4285.5549232276. The cubic root of 18365981 is about 263.8384236663.

The spelling of 18365981 in words is "eighteen million, three hundred sixty-five thousand, nine hundred eighty-one".