21011011709 has 2 divisors, whose sum is σ = 21011011710. Its totient is φ = 21011011708.

The previous prime is 21011011643. The next prime is 21011011711. The reversal of 21011011709 is 90711011012.

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., 16946311684 + 4064700025 = 130178^2 + 63755^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011011709 is a prime.

It is a super-2 number, since 2×21011011709² (a number of 21 digits) contains 22 as substring.

Together with 21011011711, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011011759) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505505854 + 10505505855.

It is an arithmetic number, because the mean of its divisors is an integer number (10505505855).

Almost surely, 2^21011011709 is an apocalyptic number.

It is an amenable number.

21011011709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011011709 is an equidigital number, since it uses as much as digits as its factorization.

21011011709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 126, while the sum is 23.

The spelling of 21011011709 in words is "twenty-one billion, eleven million, eleven thousand, seven hundred nine".