21856569640 has 16 divisors (see below), whose sum is σ = 49177281780. Its totient is φ = 8742627840.

The previous prime is 21856569601. The next prime is 21856569667. The reversal of 21856569640 is 4696565812.

It can be written as a sum of positive squares in 2 ways, for example, as 21201107236 + 655462404 = 145606^2 + 25602^2 .

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 273207081 + ... + 273207160.

Almost surely, 2^21856569640 is an apocalyptic number.

21856569640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21856569640 is an abundant number, since it is smaller than the sum of its proper divisors (27320712140).

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

21856569640 is a wasteful number, since it uses less digits than its factorization.

21856569640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546414252 (or 546414248 counting only the distinct ones).

The product of its (nonzero) digits is 3110400, while the sum is 52.

The spelling of 21856569640 in words is "twenty-one billion, eight hundred fifty-six million, five hundred sixty-nine thousand, six hundred forty".