16559951221 has 12 divisors (see below), whose sum is σ = 18245552332. Its totient is φ = 15018696000.

The previous prime is 16559951207. The next prime is 16559951249. The reversal of 16559951221 is 12215995561.

It can be written as a sum of positive squares in 2 ways, for example, as 3787787025 + 12772164196 = 61545^2 + 113014^2 .

It is not a de Polignac number, because 16559951221 - 2⁹ = 16559950709 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 (16559951251) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 111600 + ... + 213481.

Almost surely, 2^16559951221 is an apocalyptic number.

16559951221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16559951221 is a deficient number, since it is larger than the sum of its proper divisors (1685601111).

16559951221 is a wasteful number, since it uses less digits than its factorization.

16559951221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325524 (or 325513 counting only the distinct ones).

The product of its digits is 243000, while the sum is 46.

The spelling of 16559951221 in words is "sixteen billion, five hundred fifty-nine million, nine hundred fifty-one thousand, two hundred twenty-one".