21573763553 has 4 divisors (see below), whose sum is σ = 21574072980. Its totient is φ = 21573454128.

The previous prime is 21573763543. The next prime is 21573763559. The reversal of 21573763553 is 35536737512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 19953540049 + 1620223504 = 141257^2 + 40252^2 .

It is a cyclic number.

It is not a de Polignac number, because 21573763553 - 2¹⁶ = 21573698017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21573763498 and 21573763507.

It is not an unprimeable number, because it can be changed into a prime (21573763559) 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, 4451 + ... + 207767.

It is an arithmetic number, because the mean of its divisors is an integer number (5393518245).

Almost surely, 2^21573763553 is an apocalyptic number.

It is an amenable number.

21573763553 is a deficient number, since it is larger than the sum of its proper divisors (309427).

21573763553 is a wasteful number, since it uses less digits than its factorization.

21573763553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309426.

The product of its digits is 1984500, while the sum is 47.

The spelling of 21573763553 in words is "twenty-one billion, five hundred seventy-three million, seven hundred sixty-three thousand, five hundred fifty-three".