20606172721 has 2 divisors, whose sum is σ = 20606172722. Its totient is φ = 20606172720.

The previous prime is 20606172709. The next prime is 20606172751. The reversal of 20606172721 is 12727160602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18614782096 + 1991390625 = 136436^2 + 44625^2 .

It is a cyclic number.

It is not a de Polignac number, because 20606172721 - 2²⁹ = 20069301809 is a prime.

It is a super-2 number, since 2×20606172721² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20606172751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10303086360 + 10303086361.

It is an arithmetic number, because the mean of its divisors is an integer number (10303086361).

Almost surely, 2^20606172721 is an apocalyptic number.

It is an amenable number.

20606172721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20606172721 is an equidigital number, since it uses as much as digits as its factorization.

20606172721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 14112, while the sum is 34.

The spelling of 20606172721 in words is "twenty billion, six hundred six million, one hundred seventy-two thousand, seven hundred twenty-one".