21518198855 has 4 divisors (see below), whose sum is σ = 25821838632. Its totient is φ = 17214559080.

The previous prime is 21518198843. The next prime is 21518198861. The reversal of 21518198855 is 55889181512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21518198855 - 2¹² = 21518194759 is a prime.

It is a super-2 number, since 2×21518198855² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21518198797 and 21518198806.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2151819881 + ... + 2151819890.

It is an arithmetic number, because the mean of its divisors is an integer number (6455459658).

Almost surely, 2^21518198855 is an apocalyptic number.

21518198855 is a deficient number, since it is larger than the sum of its proper divisors (4303639777).

21518198855 is an equidigital number, since it uses as much as digits as its factorization.

21518198855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4303639776.

The product of its digits is 1152000, while the sum is 53.

The spelling of 21518198855 in words is "twenty-one billion, five hundred eighteen million, one hundred ninety-eight thousand, eight hundred fifty-five".