21353242661 has 4 divisors (see below), whose sum is σ = 21353568000. Its totient is φ = 21352917324.

The previous prime is 21353242639. The next prime is 21353242709. The reversal of 21353242661 is 16624235312.

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 21353242661 - 2²⁶ = 21286133797 is a prime.

It is a super-3 number, since 3×21353242661³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21353247661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25871 + ... + 208268.

It is an arithmetic number, because the mean of its divisors is an integer number (5338392000).

Almost surely, 2^21353242661 is an apocalyptic number.

It is an amenable number.

21353242661 is a deficient number, since it is larger than the sum of its proper divisors (325339).

21353242661 is an equidigital number, since it uses as much as digits as its factorization.

21353242661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325338.

The product of its digits is 51840, while the sum is 35.

Adding to 21353242661 its reverse (16624235312), we get a palindrome (37977477973).

The spelling of 21353242661 in words is "twenty-one billion, three hundred fifty-three million, two hundred forty-two thousand, six hundred sixty-one".