21507474172721 has 8 divisors (see below), whose sum is σ = 22442630020224. Its totient is φ = 20572322348160.

The previous prime is 21507474172669. The next prime is 21507474172727. The reversal of 21507474172721 is 12727147470512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21507474172721 - 2¹⁰ = 21507474171697 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21507474172721.

It is not an unprimeable number, because it can be changed into a prime (21507474172727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16134401 + ... + 17416481.

It is an arithmetic number, because the mean of its divisors is an integer number (2805328752528).

Almost surely, 2^{21507474172721} is an apocalyptic number.

It is an amenable number.

21507474172721 is a deficient number, since it is larger than the sum of its proper divisors (935155847503).

21507474172721 is a wasteful number, since it uses less digits than its factorization.

21507474172721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2011471.

The product of its (nonzero) digits is 1536640, while the sum is 50.

The spelling of 21507474172721 in words is "twenty-one trillion, five hundred seven billion, four hundred seventy-four million, one hundred seventy-two thousand, seven hundred twenty-one".