21047631171845 has 18 divisors (see below), whose sum is σ = 26830489867062. Its totient is φ = 15847496866816.

The previous prime is 21047631171803. The next prime is 21047631171857. The reversal of 21047631171845 is 54817113674012.

It can be written as a sum of positive squares in 9 ways, for example, as 138311097604 + 20909320074241 = 371902^2 + 4572671^2 .

It is not a de Polignac number, because 21047631171845 - 2³⁰ = 21046557430021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21047631171793 and 21047631171802.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 174335261 + ... + 174455949.

Almost surely, 2^{21047631171845} is an apocalyptic number.

It is an amenable number.

21047631171845 is a deficient number, since it is larger than the sum of its proper divisors (5782858695217).

21047631171845 is an frugal number, since it uses more digits than its factorization.

21047631171845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241417 (or 120711 counting only the distinct ones).

The product of its (nonzero) digits is 1128960, while the sum is 50.

The spelling of 21047631171845 in words is "twenty-one trillion, forty-seven billion, six hundred thirty-one million, one hundred seventy-one thousand, eight hundred forty-five".