21967709 has 2 divisors, whose sum is σ = 21967710. Its totient is φ = 21967708.

The previous prime is 21967669. The next prime is 21967717. The reversal of 21967709 is 90776912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11868025 + 10099684 = 3445^2 + 3178^2 .

It is a cyclic number.

It is not a de Polignac number, because 21967709 - 2¹⁶ = 21902173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21967739) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10983854 + 10983855.

It is an arithmetic number, because the mean of its divisors is an integer number (10983855).

Almost surely, 2^21967709 is an apocalyptic number.

It is an amenable number.

21967709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21967709 is an equidigital number, since it uses as much as digits as its factorization.

21967709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 47628, while the sum is 41.

The square root of 21967709 is about 4686.9722636261. The cubic root of 21967709 is about 280.0667740405.

The spelling of 21967709 in words is "twenty-one million, nine hundred sixty-seven thousand, seven hundred nine".