161221 has 2 divisors, whose sum is σ = 161222. Its totient is φ = 161220.

The previous prime is 161201. The next prime is 161233. The reversal of 161221 is 122161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 148225 + 12996 = 385^2 + 114^2 .

It is a cyclic number.

It is not a de Polignac number, because 161221 - 2⁷ = 161093 is a prime.

161221 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80610 + 80611.

It is an arithmetic number, because the mean of its divisors is an integer number (80611).

2¹⁶¹²²¹ is an apocalyptic number.

It is an amenable number.

161221 is a deficient number, since it is larger than the sum of its proper divisors (1).

161221 is an equidigital number, since it uses as much as digits as its factorization.

161221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24, while the sum is 13.

The square root of 161221 is about 401.5233492588. The cubic root of 161221 is about 54.4260985282.

Adding to 161221 its reverse (122161), we get a palindrome (283382).

Subtracting from 161221 its reverse (122161), we obtain a triangular number (39060 = T₂₇₉).

The spelling of 161221 in words is "one hundred sixty-one thousand, two hundred twenty-one".