21075556555581 has 16 divisors (see below), whose sum is σ = 30662404027200. Its totient is φ = 12770127480320.

The previous prime is 21075556555553. The next prime is 21075556555621. The reversal of 21075556555581 is 18555565557012.

It is a cyclic number.

It is not a de Polignac number, because 21075556555581 - 2²⁵ = 21075523001149 is a prime.

It is a super-2 number, since 2×21075556555581² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21075556556581) 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, 73281780 + ... + 73568813.

It is an arithmetic number, because the mean of its divisors is an integer number (1916400251700).

Almost surely, 2^{21075556555581} is an apocalyptic number.

It is an amenable number.

21075556555581 is a deficient number, since it is larger than the sum of its proper divisors (9586847471619).

21075556555581 is a wasteful number, since it uses less digits than its factorization.

21075556555581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146854956.

The product of its (nonzero) digits is 52500000, while the sum is 60.

The spelling of 21075556555581 in words is "twenty-one trillion, seventy-five billion, five hundred fifty-six million, five hundred fifty-five thousand, five hundred eighty-one".