21224545516561 has 24 divisors (see below), whose sum is σ = 22493563820840. Its totient is φ = 20021717396736.

The previous prime is 21224545516457. The next prime is 21224545516567. The reversal of 21224545516561 is 16561554542212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1146439176961 + 20078106339600 = 1070719^2 + 4480860^2 .

It is not a de Polignac number, because 21224545516561 - 2⁹ = 21224545516049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21224545516567) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 555640915 + ... + 555679111.

Almost surely, 2^{21224545516561} is an apocalyptic number.

It is an amenable number.

21224545516561 is a deficient number, since it is larger than the sum of its proper divisors (1269018304279).

21224545516561 is a wasteful number, since it uses less digits than its factorization.

21224545516561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52705 (or 52682 counting only the distinct ones).

The product of its digits is 2880000, while the sum is 49.

The spelling of 21224545516561 in words is "twenty-one trillion, two hundred twenty-four billion, five hundred forty-five million, five hundred sixteen thousand, five hundred sixty-one".