16121177221 has 4 divisors (see below), whose sum is σ = 16121634444. Its totient is φ = 16120720000.

The previous prime is 16121177207. The next prime is 16121177249. The reversal of 16121177221 is 12277112161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12277112161 = 3251 ⋅3776411.

It can be written as a sum of positive squares in 2 ways, for example, as 7024786596 + 9096390625 = 83814^2 + 95375^2 .

It is a cyclic number.

It is not a de Polignac number, because 16121177221 - 2¹¹ = 16121175173 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 (16121177251) 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, 170860 + ... + 247861.

It is an arithmetic number, because the mean of its divisors is an integer number (4030408611).

Almost surely, 2^16121177221 is an apocalyptic number.

It is an amenable number.

16121177221 is a deficient number, since it is larger than the sum of its proper divisors (457223).

16121177221 is an equidigital number, since it uses as much as digits as its factorization.

16121177221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457222.

The product of its digits is 2352, while the sum is 31.

Adding to 16121177221 its reverse (12277112161), we get a palindrome (28398289382).

The spelling of 16121177221 in words is "sixteen billion, one hundred twenty-one million, one hundred seventy-seven thousand, two hundred twenty-one".