21451905005 has 18 divisors (see below), whose sum is σ = 27352710846. Its totient is φ = 16147830528.

The previous prime is 21451905001. The next prime is 21451905053. The reversal of 21451905005 is 50050915412.

It can be written as a sum of positive squares in 9 ways, for example, as 5305374244 + 16146530761 = 72838^2 + 127069^2 .

It is not a de Polignac number, because 21451905005 - 2² = 21451905001 is a prime.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21451905001) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 5565659 + ... + 5569511.

It is an arithmetic number, because the mean of its divisors is an integer number (1519595047).

Almost surely, 2^21451905005 is an apocalyptic number.

It is an amenable number.

21451905005 is a deficient number, since it is larger than the sum of its proper divisors (5900805841).

21451905005 is an frugal number, since it uses more digits than its factorization.

21451905005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7745 (or 3875 counting only the distinct ones).

The product of its (nonzero) digits is 9000, while the sum is 32.

The spelling of 21451905005 in words is "twenty-one billion, four hundred fifty-one million, nine hundred five thousand, five".