172721 has 2 divisors, whose sum is σ = 172722. Its totient is φ = 172720.

The previous prime is 172717. The next prime is 172741. The reversal of 172721 is 127271.

It is an a-pointer prime, because the next prime (172741) can be obtained adding 172721 to its sum of digits (20).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 115600 + 57121 = 340^2 + 239^2 .

It is an emirp because it is prime and its reverse (127271) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 172721 - 2² = 172717 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 172693 and 172702.

It is not a weakly prime, because it can be changed into another prime (172741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86360 + 86361.

It is an arithmetic number, because the mean of its divisors is an integer number (86361).

2¹⁷²⁷²¹ is an apocalyptic number.

It is an amenable number.

172721 is a deficient number, since it is larger than the sum of its proper divisors (1).

172721 is an equidigital number, since it uses as much as digits as its factorization.

172721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 196, while the sum is 20.

The square root of 172721 is about 415.5971607218. The cubic root of 172721 is about 55.6905766188.

Adding to 172721 its reverse (127271), we get a palindrome (299992).

The spelling of 172721 in words is "one hundred seventy-two thousand, seven hundred twenty-one", and thus it is an iban number.