18618781 has 2 divisors, whose sum is σ = 18618782. Its totient is φ = 18618780.

The previous prime is 18618763. The next prime is 18618811. The reversal of 18618781 is 18781681.

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., 17388900 + 1229881 = 4170^2 + 1109^2 .

It is a cyclic number.

It is not a de Polignac number, because 18618781 - 2⁷ = 18618653 is a prime.

It is a super-2 number, since 2×18618781² = 693318011851922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18618731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9309390 + 9309391.

It is an arithmetic number, because the mean of its divisors is an integer number (9309391).

Almost surely, 2^18618781 is an apocalyptic number.

It is an amenable number.

18618781 is a deficient number, since it is larger than the sum of its proper divisors (1).

18618781 is an equidigital number, since it uses as much as digits as its factorization.

18618781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21504, while the sum is 40.

The square root of 18618781 is about 4314.9485512576. The cubic root of 18618781 is about 265.0434531806.

The spelling of 18618781 in words is "eighteen million, six hundred eighteen thousand, seven hundred eighty-one".