21745715678185 has 16 divisors (see below), whose sum is σ = 26995796024400. Its totient is φ = 16795997268736.

The previous prime is 21745715678179. The next prime is 21745715678189. The reversal of 21745715678185 is 58187651754712.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 207911376729 + 21537804301456 = 455973^2 + 4640884^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21745715678185 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21745715678185.

It is not an unprimeable number, because it can be changed into a prime (21745715678189) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 442311 + ... + 6609619.

It is an arithmetic number, because the mean of its divisors is an integer number (1687237251525).

Almost surely, 2^{21745715678185} is an apocalyptic number.

It is an amenable number.

21745715678185 is a deficient number, since it is larger than the sum of its proper divisors (5250080346215).

21745715678185 is a wasteful number, since it uses less digits than its factorization.

21745715678185 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6191660.

The product of its digits is 131712000, while the sum is 67.

The spelling of 21745715678185 in words is "twenty-one trillion, seven hundred forty-five billion, seven hundred fifteen million, six hundred seventy-eight thousand, one hundred eighty-five".