21006259709 has 2 divisors, whose sum is σ = 21006259710. Its totient is φ = 21006259708.

The previous prime is 21006259607. The next prime is 21006259739. The reversal of 21006259709 is 90795260012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18747634084 + 2258625625 = 136922^2 + 47525^2 .

It is a cyclic number.

It is not a de Polignac number, because 21006259709 - 2⁸ = 21006259453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21006259739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503129854 + 10503129855.

It is an arithmetic number, because the mean of its divisors is an integer number (10503129855).

Almost surely, 2^21006259709 is an apocalyptic number.

It is an amenable number.

21006259709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006259709 is an equidigital number, since it uses as much as digits as its factorization.

21006259709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 68040, while the sum is 41.

The spelling of 21006259709 in words is "twenty-one billion, six million, two hundred fifty-nine thousand, seven hundred nine".