21555306553 has 16 divisors (see below), whose sum is σ = 25037242560. Its totient is φ = 18339980800.

The previous prime is 21555306551. The next prime is 21555306613. The reversal of 21555306553 is 35560355512.

It is not a de Polignac number, because 21555306553 - 2¹ = 21555306551 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21555306551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 288508 + ... + 355453.

It is an arithmetic number, because the mean of its divisors is an integer number (1564827660).

Almost surely, 2^21555306553 is an apocalyptic number.

It is an amenable number.

21555306553 is a deficient number, since it is larger than the sum of its proper divisors (3481936007).

21555306553 is a wasteful number, since it uses less digits than its factorization.

21555306553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 644168.

The product of its (nonzero) digits is 337500, while the sum is 40.

The spelling of 21555306553 in words is "twenty-one billion, five hundred fifty-five million, three hundred six thousand, five hundred fifty-three".