221661506551165 has 16 divisors (see below), whose sum is σ = 273986884197936. Its totient is φ = 172048278873600.

The previous prime is 221661506551159. The next prime is 221661506551253. The reversal of 221661506551165 is 561155605166122.

It can be written as a sum of positive squares in 8 ways, for example, as 55604418044569 + 166057088506596 = 7456837^2 + 12886314^2 .

It is not a de Polignac number, because 221661506551165 - 2¹¹ = 221661506549117 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2986912182 + ... + 2986986391.

It is an arithmetic number, because the mean of its divisors is an integer number (17124180262371).

Almost surely, 2^{221661506551165} is an apocalyptic number.

It is an amenable number.

221661506551165 is a deficient number, since it is larger than the sum of its proper divisors (52325377646771).

221661506551165 is a wasteful number, since it uses less digits than its factorization.

221661506551165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5973898800.

The product of its (nonzero) digits is 3240000, while the sum is 52.

The spelling of 221661506551165 in words is "two hundred twenty-one trillion, six hundred sixty-one billion, five hundred six million, five hundred fifty-one thousand, one hundred sixty-five".