21857017353557 has 4 divisors (see below), whose sum is σ = 21866599564236. Its totient is φ = 21847435142880.

The previous prime is 21857017353547. The next prime is 21857017353623. The reversal of 21857017353557 is 75535371075812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9089073306481 + 12767944047076 = 3014809^2 + 3573226^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21857017353557 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21857017353496 and 21857017353505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21857017353527) 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, 4791101918 + ... + 4791106479.

It is an arithmetic number, because the mean of its divisors is an integer number (5466649891059).

Almost surely, 2^{21857017353557} is an apocalyptic number.

It is an amenable number.

21857017353557 is a deficient number, since it is larger than the sum of its proper divisors (9582210679).

21857017353557 is an equidigital number, since it uses as much as digits as its factorization.

21857017353557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9582210678.

The product of its (nonzero) digits is 30870000, while the sum is 59.

The spelling of 21857017353557 in words is "twenty-one trillion, eight hundred fifty-seven billion, seventeen million, three hundred fifty-three thousand, five hundred fifty-seven".