21520721147663 has 4 divisors (see below), whose sum is σ = 22102362259800. Its totient is φ = 20939080035528.

The previous prime is 21520721147561. The next prime is 21520721147687. The reversal of 21520721147663 is 36674112702512.

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

It is a cyclic number.

It is not a de Polignac number, because 21520721147663 - 2³² = 21516426180367 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520721117663) 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, 290820556013 + ... + 290820556086.

It is an arithmetic number, because the mean of its divisors is an integer number (5525590564950).

Almost surely, 2^{21520721147663} is an apocalyptic number.

21520721147663 is a deficient number, since it is larger than the sum of its proper divisors (581641112137).

21520721147663 is an equidigital number, since it uses as much as digits as its factorization.

21520721147663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 581641112136.

The product of its (nonzero) digits is 846720, while the sum is 47.

The spelling of 21520721147663 in words is "twenty-one trillion, five hundred twenty billion, seven hundred twenty-one million, one hundred forty-seven thousand, six hundred sixty-three".