855515021 has 4 divisors (see below), whose sum is σ = 905839452. Its totient is φ = 805190592.

The previous prime is 855514991. The next prime is 855515039. The reversal of 855515021 is 120515558.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120515558 = 2 ⋅60257779.

It can be written as a sum of positive squares in 2 ways, for example, as 764522500 + 90992521 = 27650^2 + 9539^2 .

It is a cyclic number.

It is not a de Polignac number, because 855515021 - 2¹⁸ = 855252877 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (855515321) 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 in 3 ways as a sum of consecutive naturals, for example, 25162190 + ... + 25162223.

It is an arithmetic number, because the mean of its divisors is an integer number (226459863).

Almost surely, 2^855515021 is an apocalyptic number.

It is an amenable number.

855515021 is a deficient number, since it is larger than the sum of its proper divisors (50324431).

855515021 is a wasteful number, since it uses less digits than its factorization.

855515021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50324430.

The product of its (nonzero) digits is 10000, while the sum is 32.

The square root of 855515021 is about 29249.1883819022. The cubic root of 855515021 is about 949.3125297770.

The spelling of 855515021 in words is "eight hundred fifty-five million, five hundred fifteen thousand, twenty-one".