42171721 has 2 divisors, whose sum is σ = 42171722. Its totient is φ = 42171720.

The previous prime is 42171707. The next prime is 42171761. The reversal of 42171721 is 12717124.

42171721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 22458121 + 19713600 = 4739^2 + 4440^2 .

It is a cyclic number.

It is not a de Polignac number, because 42171721 - 2⁹ = 42171209 is a prime.

It is not a weakly prime, because it can be changed into another prime (42171761) 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, 21085860 + 21085861.

It is an arithmetic number, because the mean of its divisors is an integer number (21085861).

Almost surely, 2^42171721 is an apocalyptic number.

It is an amenable number.

42171721 is a deficient number, since it is larger than the sum of its proper divisors (1).

42171721 is an equidigital number, since it uses as much as digits as its factorization.

42171721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 784, while the sum is 25.

The square root of 42171721 is about 6493.9757467980. The cubic root of 42171721 is about 348.0757558465.

Adding to 42171721 its reverse (12717124), we get a palindrome (54888845).

The spelling of 42171721 in words is "forty-two million, one hundred seventy-one thousand, seven hundred twenty-one".