21500164036721 has 8 divisors (see below), whose sum is σ = 22442845141440. Its totient is φ = 20558140545712.

The previous prime is 21500164036697. The next prime is 21500164036753. The reversal of 21500164036721 is 12763046100512.

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 21500164036721 - 2²² = 21500159842417 is a prime.

It is a super-2 number, since 2×21500164036721² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21500164036621) 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, 164336606 + ... + 164467383.

It is an arithmetic number, because the mean of its divisors is an integer number (2805355642680).

Almost surely, 2^{21500164036721} is an apocalyptic number.

It is an amenable number.

21500164036721 is a deficient number, since it is larger than the sum of its proper divisors (942681104719).

21500164036721 is a wasteful number, since it uses less digits than its factorization.

21500164036721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 328806855.

The product of its (nonzero) digits is 60480, while the sum is 38.

The spelling of 21500164036721 in words is "twenty-one trillion, five hundred billion, one hundred sixty-four million, thirty-six thousand, seven hundred twenty-one".