171961721 has 2 divisors, whose sum is σ = 171961722. Its totient is φ = 171961720.

The previous prime is 171961717. The next prime is 171961763. The reversal of 171961721 is 127169171.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 164121721 + 7840000 = 12811^2 + 2800^2 .

It is an emirp because it is prime and its reverse (127169171) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 171961721 - 2² = 171961717 is a prime.

It is not a weakly prime, because it can be changed into another prime (171961771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85980860 + 85980861.

It is an arithmetic number, because the mean of its divisors is an integer number (85980861).

Almost surely, 2^171961721 is an apocalyptic number.

It is an amenable number.

171961721 is a deficient number, since it is larger than the sum of its proper divisors (1).

171961721 is an equidigital number, since it uses as much as digits as its factorization.

171961721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5292, while the sum is 35.

The square root of 171961721 is about 13113.4175942048. The cubic root of 171961721 is about 556.0885175995.

The spelling of 171961721 in words is "one hundred seventy-one million, nine hundred sixty-one thousand, seven hundred twenty-one".