2121856686 has 48 divisors (see below), whose sum is σ = 4732535808. Its totient is φ = 686577600.

The previous prime is 2121856679. The next prime is 2121856703. The reversal of 2121856686 is 6866581212.

2121856686 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 8 + 566 + 86 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 303571 + ... + 310481.

It is an arithmetic number, because the mean of its divisors is an integer number (98594496).

Almost surely, 2^2121856686 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2121856686, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2366267904).

2121856686 is an abundant number, since it is smaller than the sum of its proper divisors (2610679122).

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

2121856686 is a wasteful number, since it uses less digits than its factorization.

2121856686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7417 (or 7414 counting only the distinct ones).

The product of its digits is 276480, while the sum is 45.

The square root of 2121856686 is about 46063.6156418490. The cubic root of 2121856686 is about 1285.0065730661.

The spelling of 2121856686 in words is "two billion, one hundred twenty-one million, eight hundred fifty-six thousand, six hundred eighty-six".