21161661161 has 8 divisors (see below), whose sum is σ = 21889165824. Its totient is φ = 20436960960.

The previous prime is 21161661121. The next prime is 21161661167. The reversal of 21161661161 is 16116616112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21161661161 - 2¹⁰ = 21161660137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21161661167) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 685760 + ... + 715953.

It is an arithmetic number, because the mean of its divisors is an integer number (2736145728).

Almost surely, 2^21161661161 is an apocalyptic number.

It is an amenable number.

21161661161 is a deficient number, since it is larger than the sum of its proper divisors (727504663).

21161661161 is a wasteful number, since it uses less digits than its factorization.

21161661161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1402231.

The product of its digits is 2592, while the sum is 32.

The spelling of 21161661161 in words is "twenty-one billion, one hundred sixty-one million, six hundred sixty-one thousand, one hundred sixty-one".