21485805646561 has 4 divisors (see below), whose sum is σ = 21494821933312. Its totient is φ = 21476789359812.

The previous prime is 21485805646553. The next prime is 21485805646573. The reversal of 21485805646561 is 16564650858412.

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 21485805646561 - 2³ = 21485805646553 is a prime.

It is a super-2 number, since 2×21485805646561² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21485805646561.

It is not an unprimeable number, because it can be changed into a prime (21485805656561) 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, 4508139801 + ... + 4508144566.

It is an arithmetic number, because the mean of its divisors is an integer number (5373705483328).

Almost surely, 2^{21485805646561} is an apocalyptic number.

It is an amenable number.

21485805646561 is a deficient number, since it is larger than the sum of its proper divisors (9016286751).

21485805646561 is an equidigital number, since it uses as much as digits as its factorization.

21485805646561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9016286750.

The product of its (nonzero) digits is 55296000, while the sum is 61.

The spelling of 21485805646561 in words is "twenty-one trillion, four hundred eighty-five billion, eight hundred five million, six hundred forty-six thousand, five hundred sixty-one".