21566016001555 has 4 divisors (see below), whose sum is σ = 25879219201872. Its totient is φ = 17252812801240.

The previous prime is 21566016001501. The next prime is 21566016001609. The reversal of 21566016001555 is 55510061066512.

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

It is an interprime number because it is at equal distance from previous prime (21566016001501) and next prime (21566016001609).

It is not a de Polignac number, because 21566016001555 - 2⁷ = 21566016001427 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2156601600151 + ... + 2156601600160.

It is an arithmetic number, because the mean of its divisors is an integer number (6469804800468).

Almost surely, 2^{21566016001555} is an apocalyptic number.

21566016001555 is a deficient number, since it is larger than the sum of its proper divisors (4313203200317).

21566016001555 is an equidigital number, since it uses as much as digits as its factorization.

21566016001555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4313203200316.

The product of its (nonzero) digits is 270000, while the sum is 43.

The spelling of 21566016001555 in words is "twenty-one trillion, five hundred sixty-six billion, sixteen million, one thousand, five hundred fifty-five".