20106721 has 2 divisors, whose sum is σ = 20106722. Its totient is φ = 20106720.

The previous prime is 20106683. The next prime is 20106727. The reversal of 20106721 is 12760102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13242321 + 6864400 = 3639^2 + 2620^2 .

It is a cyclic number.

It is not a de Polignac number, because 20106721 - 2²¹ = 18009569 is a prime.

It is a super-3 number, since 3×20106721³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (20106727) 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 as a sum of consecutive naturals, namely, 10053360 + 10053361.

It is an arithmetic number, because the mean of its divisors is an integer number (10053361).

Almost surely, 2^20106721 is an apocalyptic number.

It is an amenable number.

20106721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20106721 is an equidigital number, since it uses as much as digits as its factorization.

20106721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 20106721 is about 4484.0518507261. The cubic root of 20106721 is about 271.9237143695.

Adding to 20106721 its reverse (12760102), we get a palindrome (32866823).

The spelling of 20106721 in words is "twenty million, one hundred six thousand, seven hundred twenty-one".