204213721 has 2 divisors, whose sum is σ = 204213722. Its totient is φ = 204213720.

The previous prime is 204213703. The next prime is 204213733. The reversal of 204213721 is 127312402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 202663696 + 1550025 = 14236^2 + 1245^2 .

It is a cyclic number.

It is not a de Polignac number, because 204213721 - 2⁷ = 204213593 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 204213692 and 204213701.

It is not a weakly prime, because it can be changed into another prime (204219721) 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, 102106860 + 102106861.

It is an arithmetic number, because the mean of its divisors is an integer number (102106861).

Almost surely, 2^204213721 is an apocalyptic number.

It is an amenable number.

204213721 is a deficient number, since it is larger than the sum of its proper divisors (1).

204213721 is an equidigital number, since it uses as much as digits as its factorization.

204213721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 204213721 is about 14290.3366300448. The cubic root of 204213721 is about 588.8820359803.

It can be divided in two parts, 20421 and 3721, that added together give a palindrome (24142).

The spelling of 204213721 in words is "two hundred four million, two hundred thirteen thousand, seven hundred twenty-one".