21566840255511 has 4 divisors (see below), whose sum is σ = 28755787007352. Its totient is φ = 14377893503672.

The previous prime is 21566840255497. The next prime is 21566840255567. The reversal of 21566840255511 is 11555204866512.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21566840255511 - 2⁷ = 21566840255383 is a prime.

It is a super-2 number, since 2×21566840255511² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21566840254511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3594473375916 + ... + 3594473375921.

It is an arithmetic number, because the mean of its divisors is an integer number (7188946751838).

Almost surely, 2^{21566840255511} is an apocalyptic number.

21566840255511 is a deficient number, since it is larger than the sum of its proper divisors (7188946751841).

21566840255511 is an equidigital number, since it uses as much as digits as its factorization.

21566840255511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7188946751840.

The product of its (nonzero) digits is 2880000, while the sum is 51.

The spelling of 21566840255511 in words is "twenty-one trillion, five hundred sixty-six billion, eight hundred forty million, two hundred fifty-five thousand, five hundred eleven".