16161221 has 4 divisors (see below), whose sum is σ = 16435200. Its totient is φ = 15887244.

The previous prime is 16161209. The next prime is 16161253. The reversal of 16161221 is 12216161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 16161221 - 2¹⁴ = 16144837 is a prime.

It is a super-2 number, since 2×16161221² = 522370128421682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16161193 and 16161202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16161121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136901 + ... + 137018.

It is an arithmetic number, because the mean of its divisors is an integer number (4108800).

Almost surely, 2^16161221 is an apocalyptic number.

It is an amenable number.

16161221 is a deficient number, since it is larger than the sum of its proper divisors (273979).

16161221 is an equidigital number, since it uses as much as digits as its factorization.

16161221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273978.

The product of its digits is 144, while the sum is 20.

The square root of 16161221 is about 4020.1021131310. The cubic root of 16161221 is about 252.8277402813.

Adding to 16161221 its reverse (12216161), we get a palindrome (28377382).

The spelling of 16161221 in words is "sixteen million, one hundred sixty-one thousand, two hundred twenty-one".