21818201 has 2 divisors, whose sum is σ = 21818202. Its totient is φ = 21818200.

The previous prime is 21818171. The next prime is 21818207. The reversal of 21818201 is 10281812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13690000 + 8128201 = 3700^2 + 2851^2 .

It is a cyclic number.

It is not a de Polignac number, because 21818201 - 2¹⁸ = 21556057 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21818207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909100 + 10909101.

It is an arithmetic number, because the mean of its divisors is an integer number (10909101).

Almost surely, 2^21818201 is an apocalyptic number.

It is an amenable number.

21818201 is a deficient number, since it is larger than the sum of its proper divisors (1).

21818201 is an equidigital number, since it uses as much as digits as its factorization.

21818201 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 23.

The square root of 21818201 is about 4670.9957182597. The cubic root of 21818201 is about 279.4299669967.

The spelling of 21818201 in words is "twenty-one million, eight hundred eighteen thousand, two hundred one".