21645277205761 has 4 divisors (see below), whose sum is σ = 23613029679024. Its totient is φ = 19677524732500.

The previous prime is 21645277205759. The next prime is 21645277205771. The reversal of 21645277205761 is 16750277254612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21645277205761 - 2¹ = 21645277205759 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21645277205711) by changing a digit.

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, 983876236615 + ... + 983876236636.

It is an arithmetic number, because the mean of its divisors is an integer number (5903257419756).

Almost surely, 2^{21645277205761} is an apocalyptic number.

It is an amenable number.

21645277205761 is a deficient number, since it is larger than the sum of its proper divisors (1967752473263).

21645277205761 is a wasteful number, since it uses less digits than its factorization.

21645277205761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1967752473262.

The product of its (nonzero) digits is 9878400, while the sum is 55.

The spelling of 21645277205761 in words is "twenty-one trillion, six hundred forty-five billion, two hundred seventy-seven million, two hundred five thousand, seven hundred sixty-one".