20126721 has 4 divisors (see below), whose sum is σ = 26835632. Its totient is φ = 13417812.

The previous prime is 20126713. The next prime is 20126731. The reversal of 20126721 is 12762102.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20126721 - 2³ = 20126713 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20126731) 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, 3354451 + ... + 3354456.

It is an arithmetic number, because the mean of its divisors is an integer number (6708908).

Almost surely, 2^20126721 is an apocalyptic number.

It is an amenable number.

20126721 is a deficient number, since it is larger than the sum of its proper divisors (6708911).

20126721 is an equidigital number, since it uses as much as digits as its factorization.

20126721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6708910.

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 20126721 is about 4486.2814222917. The cubic root of 20126721 is about 272.0138446312.

Adding to 20126721 its reverse (12762102), we get a palindrome (32888823).

The spelling of 20126721 in words is "twenty million, one hundred twenty-six thousand, seven hundred twenty-one".