21042595665 has 256 divisors, whose sum is σ = 51325747200. Its totient is φ = 7915843584.

The previous prime is 21042595643. The next prime is 21042595669. The reversal of 21042595665 is 56659524012.

21042595665 is a `hidden beast` number, since 2 + 10 + 42 + 595 + 6 + 6 + 5 = 666.

It is not a de Polignac number, because 21042595665 - 2⁷ = 21042595537 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 21042595665.

It is not an unprimeable number, because it can be changed into a prime (21042595669) 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 255 ways as a sum of consecutive naturals, for example, 3965404 + ... + 3970706.

It is an arithmetic number, because the mean of its divisors is an integer number (200491200).

Almost surely, 2^21042595665 is an apocalyptic number.

It is an amenable number.

21042595665 is an abundant number, since it is smaller than the sum of its proper divisors (30283151535).

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

21042595665 is a wasteful number, since it uses less digits than its factorization.

21042595665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5373 (or 5367 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 45.

The spelling of 21042595665 in words is "twenty-one billion, forty-two million, five hundred ninety-five thousand, six hundred sixty-five".