21603882561 has 4 divisors (see below), whose sum is σ = 28805176752. Its totient is φ = 14402588372.

The previous prime is 21603882541. The next prime is 21603882577. The reversal of 21603882561 is 16528830612.

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 21603882561 - 2⁹ = 21603882049 is a prime.

It is a super-3 number, since 3×21603882561³ (a number of 32 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21603882541) 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, 3600647091 + ... + 3600647096.

It is an arithmetic number, because the mean of its divisors is an integer number (7201294188).

Almost surely, 2^21603882561 is an apocalyptic number.

It is an amenable number.

21603882561 is a deficient number, since it is larger than the sum of its proper divisors (7201294191).

21603882561 is an equidigital number, since it uses as much as digits as its factorization.

21603882561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7201294190.

The product of its (nonzero) digits is 138240, while the sum is 42.

The spelling of 21603882561 in words is "twenty-one billion, six hundred three million, eight hundred eighty-two thousand, five hundred sixty-one".