21571578644 has 24 divisors (see below), whose sum is σ = 47065263168. Its totient is φ = 8404511040.

The previous prime is 21571578641. The next prime is 21571578649. The reversal of 21571578644 is 44687517512.

It is a junction number, because it is equal to n+sod(n) for n = 21571578592 and 21571578601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21571578641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35018489 + ... + 35019104.

It is an arithmetic number, because the mean of its divisors is an integer number (1961052632).

Almost surely, 2^21571578644 is an apocalyptic number.

It is an amenable number.

21571578644 is an abundant number, since it is smaller than the sum of its proper divisors (25493684524).

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

21571578644 is a wasteful number, since it uses less digits than its factorization.

21571578644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70037615 (or 70037613 counting only the distinct ones).

The product of its digits is 1881600, while the sum is 50.

The spelling of 21571578644 in words is "twenty-one billion, five hundred seventy-one million, five hundred seventy-eight thousand, six hundred forty-four".