21715172121 has 16 divisors (see below), whose sum is σ = 29054376000. Its totient is φ = 14426462400.

The previous prime is 21715172119. The next prime is 21715172123. The reversal of 21715172121 is 12127151712.

It is an interprime number because it is at equal distance from previous prime (21715172119) and next prime (21715172123).

It is not a de Polignac number, because 21715172121 - 2¹ = 21715172119 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21715172123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1039051 + ... + 1059743.

It is an arithmetic number, because the mean of its divisors is an integer number (1815898500).

Almost surely, 2^21715172121 is an apocalyptic number.

It is an amenable number.

21715172121 is a deficient number, since it is larger than the sum of its proper divisors (7339203879).

21715172121 is a wasteful number, since it uses less digits than its factorization.

21715172121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21896.

The product of its digits is 1960, while the sum is 30.

The spelling of 21715172121 in words is "twenty-one billion, seven hundred fifteen million, one hundred seventy-two thousand, one hundred twenty-one".