21604563601 has 4 divisors (see below), whose sum is σ = 21864859632. Its totient is φ = 21344267572.

The previous prime is 21604563599. The next prime is 21604563641. The reversal of 21604563601 is 10636540612.

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 21604563601 - 2¹ = 21604563599 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21604563641) 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 3 ways as a sum of consecutive naturals, for example, 130147891 + ... + 130148056.

It is an arithmetic number, because the mean of its divisors is an integer number (5466214908).

Almost surely, 2^21604563601 is an apocalyptic number.

It is an amenable number.

21604563601 is a deficient number, since it is larger than the sum of its proper divisors (260296031).

21604563601 is an equidigital number, since it uses as much as digits as its factorization.

21604563601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 260296030.

The product of its (nonzero) digits is 25920, while the sum is 34.

The spelling of 21604563601 in words is "twenty-one billion, six hundred four million, five hundred sixty-three thousand, six hundred one".