21221366011165 has 4 divisors (see below), whose sum is σ = 25465639213404. Its totient is φ = 16977092808928.

The previous prime is 21221366011133. The next prime is 21221366011171. The reversal of 21221366011165 is 56111066312212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14934777618916 + 6286588392249 = 3864554^2 + 2507307^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221366011165 - 2⁵ = 21221366011133 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 3 ways as a sum of consecutive naturals, for example, 2122136601112 + ... + 2122136601121.

It is an arithmetic number, because the mean of its divisors is an integer number (6366409803351).

Almost surely, 2^{21221366011165} is an apocalyptic number.

It is an amenable number.

21221366011165 is a deficient number, since it is larger than the sum of its proper divisors (4244273202239).

21221366011165 is an equidigital number, since it uses as much as digits as its factorization.

21221366011165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4244273202238.

The product of its (nonzero) digits is 25920, while the sum is 37.

The spelling of 21221366011165 in words is "twenty-one trillion, two hundred twenty-one billion, three hundred sixty-six million, eleven thousand, one hundred sixty-five".