857866621 has 2 divisors, whose sum is σ = 857866622. Its totient is φ = 857866620.

The previous prime is 857866619. The next prime is 857866649. The reversal of 857866621 is 126668758.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 627252025 + 230614596 = 25045^2 + 15186^2 .

It is a cyclic number.

It is not a de Polignac number, because 857866621 - 2¹ = 857866619 is a prime.

Together with 857866619, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (857866021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428933310 + 428933311.

It is an arithmetic number, because the mean of its divisors is an integer number (428933311).

Almost surely, 2^857866621 is an apocalyptic number.

It is an amenable number.

857866621 is a deficient number, since it is larger than the sum of its proper divisors (1).

857866621 is an equidigital number, since it uses as much as digits as its factorization.

857866621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 967680, while the sum is 49.

The square root of 857866621 is about 29289.3602012745. The cubic root of 857866621 is about 950.1815427754.

The spelling of 857866621 in words is "eight hundred fifty-seven million, eight hundred sixty-six thousand, six hundred twenty-one".