21201689 has 2 divisors, whose sum is σ = 21201690. Its totient is φ = 21201688.

The previous prime is 21201679. The next prime is 21201707. The reversal of 21201689 is 98610212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15272464 + 5929225 = 3908^2 + 2435^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201689 - 2⁴ = 21201673 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21201619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600844 + 10600845.

It is an arithmetic number, because the mean of its divisors is an integer number (10600845).

Almost surely, 2^21201689 is an apocalyptic number.

It is an amenable number.

21201689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201689 is an equidigital number, since it uses as much as digits as its factorization.

21201689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21201689 is about 4604.5291833151. The cubic root of 21201689 is about 276.7728504855.

The spelling of 21201689 in words is "twenty-one million, two hundred one thousand, six hundred eighty-nine".