21211009 has 2 divisors, whose sum is σ = 21211010. Its totient is φ = 21211008.

The previous prime is 21210989. The next prime is 21211013. The reversal of 21211009 is 90011212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17098225 + 4112784 = 4135^2 + 2028^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211009 - 2⁷ = 21210881 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21210983 and 21211001.

It is not a weakly prime, because it can be changed into another prime (21211039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605504 + 10605505.

It is an arithmetic number, because the mean of its divisors is an integer number (10605505).

Almost surely, 2^21211009 is an apocalyptic number.

It is an amenable number.

21211009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211009 is an equidigital number, since it uses as much as digits as its factorization.

21211009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 16.

The square root of 21211009 is about 4605.5411191303. The cubic root of 21211009 is about 276.8133998505.

The spelling of 21211009 in words is "twenty-one million, two hundred eleven thousand, nine".