161391221 has 8 divisors (see below), whose sum is σ = 162493440. Its totient is φ = 160293312.

The previous prime is 161391199. The next prime is 161391227. The reversal of 161391221 is 122193161.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161391221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161391227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 107645 + ... + 109133.

It is an arithmetic number, because the mean of its divisors is an integer number (20311680).

Almost surely, 2^161391221 is an apocalyptic number.

It is an amenable number.

161391221 is a deficient number, since it is larger than the sum of its proper divisors (1102219).

161391221 is a wasteful number, since it uses less digits than its factorization.

161391221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2155.

The product of its digits is 648, while the sum is 26.

The square root of 161391221 is about 12703.9844537059. The cubic root of 161391221 is about 544.4524658435.

The spelling of 161391221 in words is "one hundred sixty-one million, three hundred ninety-one thousand, two hundred twenty-one".