205700021 has 2 divisors, whose sum is σ = 205700022. Its totient is φ = 205700020.

The previous prime is 205700009. The next prime is 205700029. The reversal of 205700021 is 120007502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 120340900 + 85359121 = 10970^2 + 9239^2 .

It is a cyclic number.

It is not a de Polignac number, because 205700021 - 2¹⁴ = 205683637 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205700029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102850010 + 102850011.

It is an arithmetic number, because the mean of its divisors is an integer number (102850011).

Almost surely, 2^205700021 is an apocalyptic number.

It is an amenable number.

205700021 is a deficient number, since it is larger than the sum of its proper divisors (1).

205700021 is an equidigital number, since it uses as much as digits as its factorization.

205700021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 205700021 is about 14342.2460235488. The cubic root of 205700021 is about 590.3072430203.

Adding to 205700021 its reverse (120007502), we get a palindrome (325707523).

The spelling of 205700021 in words is "two hundred five million, seven hundred thousand, twenty-one".