16611782221 has 4 divisors (see below), whose sum is σ = 16612467552. Its totient is φ = 16611096892.

The previous prime is 16611782183. The next prime is 16611782267. The reversal of 16611782221 is 12228711661.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12228711661 = 23789 ⋅514049.

It is a cyclic number.

It is not a de Polignac number, because 16611782221 - 2¹¹ = 16611780173 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 (16611782321) 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, 304921 + ... + 355246.

It is an arithmetic number, because the mean of its divisors is an integer number (4153116888).

Almost surely, 2^16611782221 is an apocalyptic number.

It is an amenable number.

16611782221 is a deficient number, since it is larger than the sum of its proper divisors (685331).

16611782221 is an equidigital number, since it uses as much as digits as its factorization.

16611782221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 685330.

The product of its digits is 16128, while the sum is 37.

The spelling of 16611782221 in words is "sixteen billion, six hundred eleven million, seven hundred eighty-two thousand, two hundred twenty-one".