21172480721 has 16 divisors (see below), whose sum is σ = 24289993728. Its totient is φ = 18078325200.

The previous prime is 21172480687. The next prime is 21172480723. The reversal of 21172480721 is 12708427112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21172480721 - 2³⁴ = 3992611537 is a prime.

It is a super-2 number, since 2×21172480721² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21172480723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2005226 + ... + 2015756.

It is an arithmetic number, because the mean of its divisors is an integer number (1518124608).

Almost surely, 2^21172480721 is an apocalyptic number.

It is an amenable number.

21172480721 is a deficient number, since it is larger than the sum of its proper divisors (3117513007).

21172480721 is a wasteful number, since it uses less digits than its factorization.

21172480721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11612.

The product of its (nonzero) digits is 12544, while the sum is 35.

The spelling of 21172480721 in words is "twenty-one billion, one hundred seventy-two million, four hundred eighty thousand, seven hundred twenty-one".