21989207 has 2 divisors, whose sum is σ = 21989208. Its totient is φ = 21989206.

The previous prime is 21989203. The next prime is 21989237. The reversal of 21989207 is 70298912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21989207 - 2² = 21989203 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21989203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10994603 + 10994604.

It is an arithmetic number, because the mean of its divisors is an integer number (10994604).

Almost surely, 2^21989207 is an apocalyptic number.

21989207 is a deficient number, since it is larger than the sum of its proper divisors (1).

21989207 is an equidigital number, since it uses as much as digits as its factorization.

21989207 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 21989207 is about 4689.2650810122. The cubic root of 21989207 is about 280.1581037362.

The spelling of 21989207 in words is "twenty-one million, nine hundred eighty-nine thousand, two hundred seven".