21185405243451 has 6 divisors (see below), whose sum is σ = 30601140907220. Its totient is φ = 14123603495628.

The previous prime is 21185405243447. The next prime is 21185405243503. The reversal of 21185405243451 is 15434250458112.

21185405243451 is a `hidden beast` number, since 2 + 1 + 1 + 8 + 5 + 40 + 524 + 34 + 51 = 666.

It is not a de Polignac number, because 21185405243451 - 2² = 21185405243447 is a prime.

It is a super-2 number, since 2×21185405243451² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21185405243397 and 21185405243406.

It is not an unprimeable number, because it can be changed into a prime (21185401243451) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1176966957961 + ... + 1176966957978.

Almost surely, 2^{21185405243451} is an apocalyptic number.

21185405243451 is a deficient number, since it is larger than the sum of its proper divisors (9415735663769).

21185405243451 is a wasteful number, since it uses less digits than its factorization.

21185405243451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2353933915945 (or 2353933915942 counting only the distinct ones).

The product of its (nonzero) digits is 768000, while the sum is 45.

The spelling of 21185405243451 in words is "twenty-one trillion, one hundred eighty-five billion, four hundred five million, two hundred forty-three thousand, four hundred fifty-one".