21566552161 has 16 divisors (see below), whose sum is σ = 27755532288. Its totient is φ = 16263003600.

The previous prime is 21566552159. The next prime is 21566552201. The reversal of 21566552161 is 16125566512.

It is a cyclic number.

It is not a de Polignac number, because 21566552161 - 2¹ = 21566552159 is a prime.

It is a super-2 number, since 2×21566552161² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21566552561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4515115 + ... + 4519888.

It is an arithmetic number, because the mean of its divisors is an integer number (1734720768).

Almost surely, 2^21566552161 is an apocalyptic number.

It is an amenable number.

21566552161 is a deficient number, since it is larger than the sum of its proper divisors (6188980127).

21566552161 is a wasteful number, since it uses less digits than its factorization.

21566552161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9035052.

The product of its digits is 108000, while the sum is 40.

The spelling of 21566552161 in words is "twenty-one billion, five hundred sixty-six million, five hundred fifty-two thousand, one hundred sixty-one".