172981 has 2 divisors, whose sum is σ = 172982. Its totient is φ = 172980.

The previous prime is 172973. The next prime is 172987. The reversal of 172981 is 189271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 128881 + 44100 = 359^2 + 210^2 .

It is an emirp because it is prime and its reverse (189271) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 172981 - 2³ = 172973 is a prime.

It is a super-2 number, since 2×172981² = 59844852722, which contains 22 as substring.

172981 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (172987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86490 + 86491.

It is an arithmetic number, because the mean of its divisors is an integer number (86491).

2¹⁷²⁹⁸¹ is an apocalyptic number.

It is an amenable number.

172981 is a deficient number, since it is larger than the sum of its proper divisors (1).

172981 is an equidigital number, since it uses as much as digits as its factorization.

172981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1008, while the sum is 28.

The square root of 172981 is about 415.9098460003. The cubic root of 172981 is about 55.7185066149.

Subtracting 172981 from its reverse (189271), we obtain a triangular number (16290 = T₁₈₀).

The spelling of 172981 in words is "one hundred seventy-two thousand, nine hundred eighty-one".