21806207 has 2 divisors, whose sum is σ = 21806208. Its totient is φ = 21806206.

The previous prime is 21806177. The next prime is 21806227. The reversal of 21806207 is 70260812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21806207 - 2⁶ = 21806143 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21806227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10903103 + 10903104.

It is an arithmetic number, because the mean of its divisors is an integer number (10903104).

Almost surely, 2^21806207 is an apocalyptic number.

21806207 is a deficient number, since it is larger than the sum of its proper divisors (1).

21806207 is an equidigital number, since it uses as much as digits as its factorization.

21806207 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21806207 is about 4669.7116613341. The cubic root of 21806207 is about 279.3787544434.

The spelling of 21806207 in words is "twenty-one million, eight hundred six thousand, two hundred seven".