18218881 has 2 divisors, whose sum is σ = 18218882. Its totient is φ = 18218880.

The previous prime is 18218867. The next prime is 18218899. The reversal of 18218881 is 18881281.

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., 17297281 + 921600 = 4159^2 + 960^2 .

It is an emirp because it is prime and its reverse (18881281) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18218881 is a prime.

It is a super-2 number, since 2×18218881² = 663855249784322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 18218881.

It is not a weakly prime, because it can be changed into another prime (18218821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9109440 + 9109441.

It is an arithmetic number, because the mean of its divisors is an integer number (9109441).

Almost surely, 2^18218881 is an apocalyptic number.

It is an amenable number.

18218881 is a deficient number, since it is larger than the sum of its proper divisors (1).

18218881 is an equidigital number, since it uses as much as digits as its factorization.

18218881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8192, while the sum is 37.

The square root of 18218881 is about 4268.3581152476. The cubic root of 18218881 is about 263.1321411843.

The spelling of 18218881 in words is "eighteen million, two hundred eighteen thousand, eight hundred eighty-one".