21518659105 has 4 divisors (see below), whose sum is σ = 25822390932. Its totient is φ = 17214927280.

The previous prime is 21518659103. The next prime is 21518659121. The reversal of 21518659105 is 50195681512.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7159190544 + 14359468561 = 84612^2 + 119831^2 .

It is not a de Polignac number, because 21518659105 - 2¹ = 21518659103 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21518659103) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2151865906 + ... + 2151865915.

It is an arithmetic number, because the mean of its divisors is an integer number (6455597733).

Almost surely, 2^21518659105 is an apocalyptic number.

It is an amenable number.

21518659105 is a deficient number, since it is larger than the sum of its proper divisors (4303731827).

21518659105 is an equidigital number, since it uses as much as digits as its factorization.

21518659105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4303731826.

The product of its (nonzero) digits is 108000, while the sum is 43.

The spelling of 21518659105 in words is "twenty-one billion, five hundred eighteen million, six hundred fifty-nine thousand, one hundred five".