20723121 has 10 divisors (see below), whose sum is σ = 30956882. Its totient is φ = 13815360.

The previous prime is 20723113. The next prime is 20723137. The reversal of 20723121 is 12132702.

It can be written as a sum of positive squares in only one way, i.e., 19847025 + 876096 = 4455^2 + 936^2 .

It is not a de Polignac number, because 20723121 - 2³ = 20723113 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20723094 and 20723103.

It is not an unprimeable number, because it can be changed into a prime (20723111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 127840 + ... + 128001.

Almost surely, 2^20723121 is an apocalyptic number.

It is an amenable number.

20723121 is a deficient number, since it is larger than the sum of its proper divisors (10233761).

20723121 is an equidigital number, since it uses as much as digits as its factorization.

20723121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255853 (or 255844 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 20723121 is about 4552.2654799561. The cubic root of 20723121 is about 274.6745284443.

Adding to 20723121 its reverse (12132702), we get a palindrome (32855823).

The spelling of 20723121 in words is "twenty million, seven hundred twenty-three thousand, one hundred twenty-one".