21806737857 has 12 divisors (see below), whose sum is σ = 31599260004. Its totient is φ = 14491376640.

The previous prime is 21806737801. The next prime is 21806737871. The reversal of 21806737857 is 75873760812.

21806737857 is a `hidden beast` number, since 218 + 0 + 6 + 7 + 378 + 57 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 2067611841 + 19739126016 = 45471^2 + 140496^2 .

It is not a de Polignac number, because 21806737857 - 2²⁴ = 21789960641 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21806737357) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3867744 + ... + 3873377.

It is an arithmetic number, because the mean of its divisors is an integer number (2633271667).

Almost surely, 2^21806737857 is an apocalyptic number.

It is an amenable number.

21806737857 is a deficient number, since it is larger than the sum of its proper divisors (9792522147).

21806737857 is a wasteful number, since it uses less digits than its factorization.

21806737857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7741440 (or 7741437 counting only the distinct ones).

The product of its (nonzero) digits is 3951360, while the sum is 54.

The spelling of 21806737857 in words is "twenty-one billion, eight hundred six million, seven hundred thirty-seven thousand, eight hundred fifty-seven".