855615821 has 2 divisors, whose sum is σ = 855615822. Its totient is φ = 855615820.

The previous prime is 855615811. The next prime is 855615833. The reversal of 855615821 is 128516558.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 794619721 + 60996100 = 28189^2 + 7810^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-855615821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (855615811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 427807910 + 427807911.

It is an arithmetic number, because the mean of its divisors is an integer number (427807911).

Almost surely, 2^855615821 is an apocalyptic number.

It is an amenable number.

855615821 is a deficient number, since it is larger than the sum of its proper divisors (1).

855615821 is an equidigital number, since it uses as much as digits as its factorization.

855615821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 96000, while the sum is 41.

The square root of 855615821 is about 29250.9114558846. The cubic root of 855615821 is about 949.3498121713.

The spelling of 855615821 in words is "eight hundred fifty-five million, six hundred fifteen thousand, eight hundred twenty-one".