21210989 has 2 divisors, whose sum is σ = 21210990. Its totient is φ = 21210988.

The previous prime is 21210979. The next prime is 21211009. The reversal of 21210989 is 98901212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10778089 + 10432900 = 3283^2 + 3230^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210989 - 2²⁰ = 20162413 is a prime.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605494 + 10605495.

It is an arithmetic number, because the mean of its divisors is an integer number (10605495).

Almost surely, 2^21210989 is an apocalyptic number.

It is an amenable number.

21210989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210989 is an equidigital number, since it uses as much as digits as its factorization.

21210989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 21210989 is about 4605.5389478323. The cubic root of 21210989 is about 276.8133128475.

The spelling of 21210989 in words is "twenty-one million, two hundred ten thousand, nine hundred eighty-nine".