21199709 has 2 divisors, whose sum is σ = 21199710. Its totient is φ = 21199708.

The previous prime is 21199681. The next prime is 21199723. The reversal of 21199709 is 90799112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21187609 + 12100 = 4603^2 + 110^2 .

It is a cyclic number.

It is not a de Polignac number, because 21199709 - 2¹² = 21195613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21199909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10599854 + 10599855.

It is an arithmetic number, because the mean of its divisors is an integer number (10599855).

Almost surely, 2^21199709 is an apocalyptic number.

It is an amenable number.

21199709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21199709 is an equidigital number, since it uses as much as digits as its factorization.

21199709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 21199709 is about 4604.3141725994. The cubic root of 21199709 is about 276.7642343904.

The spelling of 21199709 in words is "twenty-one million, one hundred ninety-nine thousand, seven hundred nine".