21818207 has 2 divisors, whose sum is σ = 21818208. Its totient is φ = 21818206.

The previous prime is 21818201. The next prime is 21818221. The reversal of 21818207 is 70281812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21818207 - 2⁸ = 21817951 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21818207.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21818201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909103 + 10909104.

It is an arithmetic number, because the mean of its divisors is an integer number (10909104).

Almost surely, 2^21818207 is an apocalyptic number.

21818207 is a deficient number, since it is larger than the sum of its proper divisors (1).

21818207 is an equidigital number, since it uses as much as digits as its factorization.

21818207 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21818207 is about 4670.9963605210. The cubic root of 21818207 is about 279.4299926111.

The spelling of 21818207 in words is "twenty-one million, eight hundred eighteen thousand, two hundred seven".