21818873 has 2 divisors, whose sum is σ = 21818874. Its totient is φ = 21818872.

The previous prime is 21818869. The next prime is 21818893. The reversal of 21818873 is 37881812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21049744 + 769129 = 4588^2 + 877^2 .

It is a cyclic number.

It is not a de Polignac number, because 21818873 - 2² = 21818869 is a prime.

It is not a weakly prime, because it can be changed into another prime (21818833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909436 + 10909437.

It is an arithmetic number, because the mean of its divisors is an integer number (10909437).

Almost surely, 2^21818873 is an apocalyptic number.

It is an amenable number.

21818873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21818873 is an equidigital number, since it uses as much as digits as its factorization.

21818873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21504, while the sum is 38.

The square root of 21818873 is about 4671.0676509766. The cubic root of 21818873 is about 279.4328357790.

It can be divided in two parts, 218 and 18873, that added together give a palindrome (19091).

The spelling of 21818873 in words is "twenty-one million, eight hundred eighteen thousand, eight hundred seventy-three".