21509901105 has 128 divisors (see below), whose sum is σ = 44172656640. Its totient is φ = 8679509760.

The previous prime is 21509901103. The next prime is 21509901107. The reversal of 21509901105 is 50110990512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21509901103) and next prime (21509901107).

It is not a de Polignac number, because 21509901105 - 2¹ = 21509901103 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21509901103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 5654134 + ... + 5657936.

It is an arithmetic number, because the mean of its divisors is an integer number (345098880).

Almost surely, 2^21509901105 is an apocalyptic number.

It is an amenable number.

21509901105 is an abundant number, since it is smaller than the sum of its proper divisors (22662755535).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21509901105 is a wasteful number, since it uses less digits than its factorization.

21509901105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3971.

The product of its (nonzero) digits is 4050, while the sum is 33.

The spelling of 21509901105 in words is "twenty-one billion, five hundred nine million, nine hundred one thousand, one hundred five".