21089719729 has 9 divisors (see below), whose sum is σ = 22838841579. Its totient is φ = 19465690920.

The previous prime is 21089719711. The next prime is 21089719753. The reversal of 21089719729 is 92791798012.

The square root of 21089719729 is 145223.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 3119781025 + 17969938704 = 55855^2 + 134052^2 .

It is not a de Polignac number, because 21089719729 - 2⁵ = 21089719697 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21089719729.

It is not an unprimeable number, because it can be changed into a prime (21089719759) 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 in 8 ways as a sum of consecutive naturals, for example, 1882314 + ... + 1893484.

Almost surely, 2^21089719729 is an apocalyptic number.

21089719729 is the 145223-rd square number.

21089719729 is the 72612-nd centered octagonal number.

It is an amenable number.

21089719729 is a deficient number, since it is larger than the sum of its proper divisors (1749121850).

21089719729 is an frugal number, since it uses more digits than its factorization.

21089719729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22368 (or 11184 counting only the distinct ones).

The product of its (nonzero) digits is 1143072, while the sum is 55.

The spelling of 21089719729 in words is "twenty-one billion, eighty-nine million, seven hundred nineteen thousand, seven hundred twenty-nine".