21175806645 has 256 divisors, whose sum is σ = 46820229120. Its totient is φ = 8862400512.

The previous prime is 21175806629. The next prime is 21175806671. The reversal of 21175806645 is 54660857112.

21175806645 is a `hidden beast` number, since 2 + 1 + 1 + 7 + 580 + 6 + 64 + 5 = 666.

It is not a de Polignac number, because 21175806645 - 2⁴ = 21175806629 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21175806645.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 166738572 + ... + 166738698.

It is an arithmetic number, because the mean of its divisors is an integer number (182891520).

Almost surely, 2^21175806645 is an apocalyptic number.

It is an amenable number.

21175806645 is an abundant number, since it is smaller than the sum of its proper divisors (25644422475).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21175806645 is a wasteful number, since it uses less digits than its factorization.

21175806645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369 (or 363 counting only the distinct ones).

The product of its (nonzero) digits is 403200, while the sum is 45.

The spelling of 21175806645 in words is "twenty-one billion, one hundred seventy-five million, eight hundred six thousand, six hundred forty-five".