21855018555 has 12 divisors (see below), whose sum is σ = 37882032240. Its totient is φ = 11656009872.

The previous prime is 21855018547. The next prime is 21855018607. The reversal of 21855018555 is 55581055812.

21855018555 is a `hidden beast` number, since 2 + 1 + 85 + 5 + 0 + 18 + 555 = 666.

It is not a de Polignac number, because 21855018555 - 2³ = 21855018547 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 485667079 = 21855018555 / (2 + 1 + 8 + 5 + 5 + 0 + 1 + 8 + 5 + 5 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 21855018555.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 242833495 + ... + 242833584.

It is an arithmetic number, because the mean of its divisors is an integer number (3156836020).

Almost surely, 2^21855018555 is an apocalyptic number.

21855018555 is a deficient number, since it is larger than the sum of its proper divisors (16027013685).

21855018555 is a wasteful number, since it uses less digits than its factorization.

21855018555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 485667090 (or 485667087 counting only the distinct ones).

The product of its (nonzero) digits is 400000, while the sum is 45.

The spelling of 21855018555 in words is "twenty-one billion, eight hundred fifty-five million, eighteen thousand, five hundred fifty-five".