21666853441 has 4 divisors (see below), whose sum is σ = 21927899952. Its totient is φ = 21405806932.

The previous prime is 21666853423. The next prime is 21666853451. The reversal of 21666853441 is 14435866612.

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 21666853441 - 2⁹ = 21666852929 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21666853391 and 21666853400.

It is not an unprimeable number, because it can be changed into a prime (21666853451) 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, 130523131 + ... + 130523296.

It is an arithmetic number, because the mean of its divisors is an integer number (5481974988).

Almost surely, 2^21666853441 is an apocalyptic number.

It is an amenable number.

21666853441 is a deficient number, since it is larger than the sum of its proper divisors (261046511).

21666853441 is an equidigital number, since it uses as much as digits as its factorization.

21666853441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261046510.

The product of its digits is 829440, while the sum is 46.

The spelling of 21666853441 in words is "twenty-one billion, six hundred sixty-six million, eight hundred fifty-three thousand, four hundred forty-one".