20129857866 has 24 divisors (see below), whose sum is σ = 43843048704. Its totient is φ = 6674820840.

The previous prime is 20129857849. The next prime is 20129857889. The reversal of 20129857866 is 66875892102.

20129857866 is a `hidden beast` number, since 2 + 0 + 1 + 2 + 9 + 8 + 578 + 66 = 666.

It is a super-2 number, since 2×20129857866² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 2924116 + ... + 2930991.

It is an arithmetic number, because the mean of its divisors is an integer number (1826793696).

Almost surely, 2^20129857866 is an apocalyptic number.

20129857866 is an abundant number, since it is smaller than the sum of its proper divisors (23713190838).

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

20129857866 is a wasteful number, since it uses less digits than its factorization.

20129857866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5855306 (or 5855303 counting only the distinct ones).

The product of its (nonzero) digits is 2903040, while the sum is 54.

The spelling of 20129857866 in words is "twenty billion, one hundred twenty-nine million, eight hundred fifty-seven thousand, eight hundred sixty-six".