21721147846873 has 4 divisors (see below), whose sum is σ = 21846703614948. Its totient is φ = 21595592078800.

The previous prime is 21721147846829. The next prime is 21721147846919. The reversal of 21721147846873 is 37864874112712.

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 20742805298329 + 978342548544 = 4554427^2 + 989112^2 .

It is a cyclic number.

It is not a de Polignac number, because 21721147846873 - 2⁹ = 21721147846361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21721147546873) 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, 62777883778 + ... + 62777884123.

It is an arithmetic number, because the mean of its divisors is an integer number (5461675903737).

Almost surely, 2^{21721147846873} is an apocalyptic number.

It is an amenable number.

21721147846873 is a deficient number, since it is larger than the sum of its proper divisors (125555768075).

21721147846873 is a wasteful number, since it uses less digits than its factorization.

21721147846873 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125555768074.

The product of its digits is 25288704, while the sum is 61.

The spelling of 21721147846873 in words is "twenty-one trillion, seven hundred twenty-one billion, one hundred forty-seven million, eight hundred forty-six thousand, eight hundred seventy-three".