20127721 has 4 divisors (see below), whose sum is σ = 20171844. Its totient is φ = 20083600.

The previous prime is 20127713. The next prime is 20127727. The reversal of 20127721 is 12772102.

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 12702096 + 7425625 = 3564^2 + 2725^2 .

It is a cyclic number.

It is not a de Polignac number, because 20127721 - 2³ = 20127713 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20127692 and 20127701.

It is not an unprimeable number, because it can be changed into a prime (20127727) 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, 21370 + ... + 22291.

It is an arithmetic number, because the mean of its divisors is an integer number (5042961).

Almost surely, 2^20127721 is an apocalyptic number.

It is an amenable number.

20127721 is a deficient number, since it is larger than the sum of its proper divisors (44123).

20127721 is an equidigital number, since it uses as much as digits as its factorization.

20127721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44122.

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 20127721 is about 4486.3928717846. The cubic root of 20127721 is about 272.0183495767.

Adding to 20127721 its reverse (12772102), we get a palindrome (32899823).

The spelling of 20127721 in words is "twenty million, one hundred twenty-seven thousand, seven hundred twenty-one".