161221586 has 4 divisors (see below), whose sum is σ = 241832382. Its totient is φ = 80610792.

The previous prime is 161221583. The next prime is 161221603. The reversal of 161221586 is 685122161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 685122161 = 26083 ⋅26267.

It can be written as a sum of positive squares in only one way, i.e., 130074025 + 31147561 = 11405^2 + 5581^2 .

It is not an unprimeable number, because it can be changed into a prime (161221583) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40305395 + ... + 40305398.

Almost surely, 2^161221586 is an apocalyptic number.

161221586 is a deficient number, since it is larger than the sum of its proper divisors (80610796).

161221586 is an equidigital number, since it uses as much as digits as its factorization.

161221586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80610795.

The product of its digits is 5760, while the sum is 32.

The square root of 161221586 is about 12697.3062497523. The cubic root of 161221586 is about 544.2616447010.

The spelling of 161221586 in words is "one hundred sixty-one million, two hundred twenty-one thousand, five hundred eighty-six".