21724016775409 has 9 divisors (see below), whose sum is σ = 23523705078219. Its totient is φ = 20052882631080.

The previous prime is 21724016775397. The next prime is 21724016775467. The reversal of 21724016775409 is 90457761042712.

It is a happy number.

The square root of 21724016775409 is 4660903.

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., 3213611949025 + 18510404826384 = 1792655^2 + 4302372^2 .

It is not a de Polignac number, because 21724016775409 - 2¹⁵ = 21724016742641 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 21724016775409.

It is not an unprimeable number, because it can be changed into a prime (21724016775809) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 60412474 + ... + 60771004.

It is an arithmetic number, because the mean of its divisors is an integer number (2613745008691).

Almost surely, 2^{21724016775409} is an apocalyptic number.

21724016775409 is the 4660903-rd square number.

21724016775409 is the 2330452-nd centered octagonal number.

It is an amenable number.

21724016775409 is a deficient number, since it is larger than the sum of its proper divisors (1799688302810).

21724016775409 is an frugal number, since it uses more digits than its factorization.

21724016775409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 717088 (or 358544 counting only the distinct ones).

The product of its (nonzero) digits is 5927040, while the sum is 55.

The spelling of 21724016775409 in words is "twenty-one trillion, seven hundred twenty-four billion, sixteen million, seven hundred seventy-five thousand, four hundred nine".