21871890856 has 16 divisors (see below), whose sum is σ = 41236371540. Its totient is φ = 10875525120.

The previous prime is 21871890853. The next prime is 21871890881. The reversal of 21871890856 is 65809817812.

It can be written as a sum of positive squares in 2 ways, for example, as 18821096100 + 3050794756 = 137190^2 + 55234^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21871890797 and 21871890806.

It is not an unprimeable number, because it can be changed into a prime (21871890853) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7551001 + ... + 7553896.

Almost surely, 2^21871890856 is an apocalyptic number.

It is an amenable number.

21871890856 is a deficient number, since it is larger than the sum of its proper divisors (19364480684).

21871890856 is a wasteful number, since it uses less digits than its factorization.

21871890856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15105084 (or 15105080 counting only the distinct ones).

The product of its (nonzero) digits is 1935360, while the sum is 55.

The spelling of 21871890856 in words is "twenty-one billion, eight hundred seventy-one million, eight hundred ninety thousand, eight hundred fifty-six".