18263981 has 4 divisors (see below), whose sum is σ = 18573600. Its totient is φ = 17954364.

The previous prime is 18263963. The next prime is 18263989. The reversal of 18263981 is 18936281.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18263981 is a prime.

It is a super-2 number, since 2×18263981² = 667146003936722, 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 (18263989) 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, 154721 + ... + 154838.

It is an arithmetic number, because the mean of its divisors is an integer number (4643400).

Almost surely, 2^18263981 is an apocalyptic number.

It is an amenable number.

18263981 is a deficient number, since it is larger than the sum of its proper divisors (309619).

18263981 is an equidigital number, since it uses as much as digits as its factorization.

18263981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309618.

The product of its digits is 20736, while the sum is 38.

The square root of 18263981 is about 4273.6379116626. The cubic root of 18263981 is about 263.3490860985.

The spelling of 18263981 in words is "eighteen million, two hundred sixty-three thousand, nine hundred eighty-one".