16404311221 has 2 divisors, whose sum is σ = 16404311222. Its totient is φ = 16404311220.

The previous prime is 16404311213. The next prime is 16404311233. The reversal of 16404311221 is 12211340461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13569920100 + 2834391121 = 116490^2 + 53239^2 .

It is a cyclic number.

It is not a de Polignac number, because 16404311221 - 2³ = 16404311213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16404311251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8202155610 + 8202155611.

It is an arithmetic number, because the mean of its divisors is an integer number (8202155611).

Almost surely, 2^16404311221 is an apocalyptic number.

It is an amenable number.

16404311221 is a deficient number, since it is larger than the sum of its proper divisors (1).

16404311221 is an equidigital number, since it uses as much as digits as its factorization.

16404311221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 25.

Adding to 16404311221 its reverse (12211340461), we get a palindrome (28615651682).

The spelling of 16404311221 in words is "sixteen billion, four hundred four million, three hundred eleven thousand, two hundred twenty-one".