21214309 has 2 divisors, whose sum is σ = 21214310. Its totient is φ = 21214308.

The previous prime is 21214273. The next prime is 21214321. The reversal of 21214309 is 90341212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15382084 + 5832225 = 3922^2 + 2415^2 .

It is a cyclic number.

It is not a de Polignac number, because 21214309 - 2¹³ = 21206117 is a prime.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21214309.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21214909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607154 + 10607155.

It is an arithmetic number, because the mean of its divisors is an integer number (10607155).

Almost surely, 2^21214309 is an apocalyptic number.

It is an amenable number.

21214309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21214309 is an equidigital number, since it uses as much as digits as its factorization.

21214309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21214309 is about 4605.8993692872. The cubic root of 21214309 is about 276.8277546109.

The spelling of 21214309 in words is "twenty-one million, two hundred fourteen thousand, three hundred nine".