21079557689 has 2 divisors, whose sum is σ = 21079557690. Its totient is φ = 21079557688.

The previous prime is 21079557683. The next prime is 21079557721. The reversal of 21079557689 is 98675597012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11468696464 + 9610861225 = 107092^2 + 98035^2 .

It is a cyclic number.

It is not a de Polignac number, because 21079557689 - 2²⁰ = 21078509113 is a prime.

It is not a weakly prime, because it can be changed into another prime (21079557683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10539778844 + 10539778845.

It is an arithmetic number, because the mean of its divisors is an integer number (10539778845).

Almost surely, 2^21079557689 is an apocalyptic number.

It is an amenable number.

21079557689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21079557689 is an equidigital number, since it uses as much as digits as its factorization.

21079557689 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9525600, while the sum is 59.

The spelling of 21079557689 in words is "twenty-one billion, seventy-nine million, five hundred fifty-seven thousand, six hundred eighty-nine".