21489588661 has 4 divisors (see below), whose sum is σ = 21895052652. Its totient is φ = 21084124672.

The previous prime is 21489588581. The next prime is 21489588691. The reversal of 21489588661 is 16688598412.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19552708561 + 1936880100 = 139831^2 + 44010^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21489588661 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21489588596 and 21489588605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21489588691) 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, 202731916 + ... + 202732021.

It is an arithmetic number, because the mean of its divisors is an integer number (5473763163).

Almost surely, 2^21489588661 is an apocalyptic number.

It is an amenable number.

21489588661 is a deficient number, since it is larger than the sum of its proper divisors (405463991).

21489588661 is an equidigital number, since it uses as much as digits as its factorization.

21489588661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 405463990.

The product of its digits is 6635520, while the sum is 58.

The spelling of 21489588661 in words is "twenty-one billion, four hundred eighty-nine million, five hundred eighty-eight thousand, six hundred sixty-one".