21555555553 has 6 divisors (see below), whose sum is σ = 25074829986. Its totient is φ = 18476190432.

The previous prime is 21555555547. The next prime is 21555555589. The reversal of 21555555553 is 35555555512.

It can be written as a sum of positive squares in only one way, i.e., 21278932129 + 276623424 = 145873^2 + 16632^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21555555553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555555653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 219954600 + ... + 219954697.

It is an arithmetic number, because the mean of its divisors is an integer number (4179138331).

Almost surely, 2^21555555553 is an apocalyptic number.

It is an amenable number.

21555555553 is a deficient number, since it is larger than the sum of its proper divisors (3519274433).

21555555553 is an equidigital number, since it uses as much as digits as its factorization.

21555555553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 439909311 (or 439909304 counting only the distinct ones).

The product of its digits is 2343750, while the sum is 46.

The spelling of 21555555553 in words is "twenty-one billion, five hundred fifty-five million, five hundred fifty-five thousand, five hundred fifty-three".