205172021 has 2 divisors, whose sum is σ = 205172022. Its totient is φ = 205172020.

The previous prime is 205172017. The next prime is 205172027. The reversal of 205172021 is 120271502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 188073796 + 17098225 = 13714^2 + 4135^2 .

It is a cyclic number.

It is not a de Polignac number, because 205172021 - 2² = 205172017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 205171984 and 205172002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205172027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102586010 + 102586011.

It is an arithmetic number, because the mean of its divisors is an integer number (102586011).

Almost surely, 2^205172021 is an apocalyptic number.

It is an amenable number.

205172021 is a deficient number, since it is larger than the sum of its proper divisors (1).

205172021 is an equidigital number, since it uses as much as digits as its factorization.

205172021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 205172021 is about 14323.8270374925. The cubic root of 205172021 is about 589.8017345883.

The spelling of 205172021 in words is "two hundred five million, one hundred seventy-two thousand, twenty-one".