20753571721 has 3 divisors (see below), whose sum is σ = 20753715783. Its totient is φ = 20753427660.

The previous prime is 20753571703. The next prime is 20753571793. The reversal of 20753571721 is 12717535702.

The square root of 20753571721 is 144061.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 2317363321 + 18436208400 = 48139^2 + 135780^2 .

It is not a de Polignac number, because 20753571721 - 2⁵ = 20753571689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20753571221) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 72031 + ... + 216091.

It is an arithmetic number, because the mean of its divisors is an integer number (6917905261).

Almost surely, 2^20753571721 is an apocalyptic number.

20753571721 is the 144061-st square number.

20753571721 is the 72031-st centered octagonal number.

It is an amenable number.

20753571721 is a deficient number, since it is larger than the sum of its proper divisors (144062).

20753571721 is an frugal number, since it uses more digits than its factorization.

20753571721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288122 (or 144061 counting only the distinct ones).

The product of its (nonzero) digits is 102900, while the sum is 40.

The spelling of 20753571721 in words is "twenty billion, seven hundred fifty-three million, five hundred seventy-one thousand, seven hundred twenty-one".