21120689 has 2 divisors, whose sum is σ = 21120690. Its totient is φ = 21120688.

The previous prime is 21120677. The next prime is 21120691. The reversal of 21120689 is 98602112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 34225 = 4592^2 + 185^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120689 - 2¹² = 21116593 is a prime.

Together with 21120691, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21120629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560344 + 10560345.

It is an arithmetic number, because the mean of its divisors is an integer number (10560345).

Almost surely, 2^21120689 is an apocalyptic number.

It is an amenable number.

21120689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120689 is an equidigital number, since it uses as much as digits as its factorization.

21120689 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 21120689 is about 4595.7250788097. The cubic root of 21120689 is about 276.4199350274.

The spelling of 21120689 in words is "twenty-one million, one hundred twenty thousand, six hundred eighty-nine".