21545572221 has 6 divisors (see below), whose sum is σ = 31121382110. Its totient is φ = 14363714808.

The previous prime is 21545572073. The next prime is 21545572241. The reversal of 21545572221 is 12227554512.

21545572221 is a `hidden beast` number, since 21 + 5 + 45 + 572 + 2 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 20466449721 + 1079122500 = 143061^2 + 32850^2 .

It is not a de Polignac number, because 21545572221 - 2¹¹ = 21545570173 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545572241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1196976226 + ... + 1196976243.

Almost surely, 2^21545572221 is an apocalyptic number.

It is an amenable number.

21545572221 is a deficient number, since it is larger than the sum of its proper divisors (9575809889).

21545572221 is a wasteful number, since it uses less digits than its factorization.

21545572221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2393952475 (or 2393952472 counting only the distinct ones).

The product of its digits is 56000, while the sum is 36.

The spelling of 21545572221 in words is "twenty-one billion, five hundred forty-five million, five hundred seventy-two thousand, two hundred twenty-one".