18423781 has 2 divisors, whose sum is σ = 18423782. Its totient is φ = 18423780.

The previous prime is 18423773. The next prime is 18423799. The reversal of 18423781 is 18732481.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17926756 + 497025 = 4234^2 + 705^2 .

It is a cyclic number.

It is not a de Polignac number, because 18423781 - 2³ = 18423773 is a prime.

It is a super-2 number, since 2×18423781² = 678871412671922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18423751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9211890 + 9211891.

It is an arithmetic number, because the mean of its divisors is an integer number (9211891).

Almost surely, 2^18423781 is an apocalyptic number.

It is an amenable number.

18423781 is a deficient number, since it is larger than the sum of its proper divisors (1).

18423781 is an equidigital number, since it uses as much as digits as its factorization.

18423781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10752, while the sum is 34.

The square root of 18423781 is about 4292.2932099287. The cubic root of 18423781 is about 264.1149111401.

The spelling of 18423781 in words is "eighteen million, four hundred twenty-three thousand, seven hundred eighty-one".