171939221 has 2 divisors, whose sum is σ = 171939222. Its totient is φ = 171939220.

The previous prime is 171939127. The next prime is 171939277. The reversal of 171939221 is 122939171.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 121330225 + 50608996 = 11015^2 + 7114^2 .

It is a cyclic number.

It is not a de Polignac number, because 171939221 - 2¹⁰ = 171938197 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (171939121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85969610 + 85969611.

It is an arithmetic number, because the mean of its divisors is an integer number (85969611).

Almost surely, 2^171939221 is an apocalyptic number.

It is an amenable number.

171939221 is a deficient number, since it is larger than the sum of its proper divisors (1).

171939221 is an equidigital number, since it uses as much as digits as its factorization.

171939221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6804, while the sum is 35.

The square root of 171939221 is about 13112.5596662132. The cubic root of 171939221 is about 556.0642630981.

Subtracting from 171939221 its reverse (122939171), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 171939221 in words is "one hundred seventy-one million, nine hundred thirty-nine thousand, two hundred twenty-one".