1721572660721 has 4 divisors (see below), whose sum is σ = 1722396776100. Its totient is φ = 1720748545344.

The previous prime is 1721572660679. The next prime is 1721572660741. The reversal of 1721572660721 is 1270662751271.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1123176040000 + 598396620721 = 1059800^2 + 773561^2 .

It is a cyclic number.

It is not a de Polignac number, because 1721572660721 - 2²² = 1721568466417 is a prime.

It is a super-3 number, since 3×1721572660721³ (a number of 38 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1721572660741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 412054556 + ... + 412058733.

It is an arithmetic number, because the mean of its divisors is an integer number (430599194025).

Almost surely, 2^{1721572660721} is an apocalyptic number.

It is an amenable number.

1721572660721 is a deficient number, since it is larger than the sum of its proper divisors (824115379).

1721572660721 is an equidigital number, since it uses as much as digits as its factorization.

1721572660721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 824115378.

The product of its (nonzero) digits is 493920, while the sum is 47.

The spelling of 1721572660721 in words is "one trillion, seven hundred twenty-one billion, five hundred seventy-two million, six hundred sixty thousand, seven hundred twenty-one".