285905021 has 4 divisors (see below), whose sum is σ = 286098012. Its totient is φ = 285712032.

The previous prime is 285905017. The next prime is 285905023. The reversal of 285905021 is 120509582.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120509582 = 2 ⋅60254791.

It can be written as a sum of positive squares in 2 ways, for example, as 130279396 + 155625625 = 11414^2 + 12475^2 .

It is a cyclic number.

It is not a de Polignac number, because 285905021 - 2² = 285905017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (285905023) 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, 94256 + ... + 97241.

It is an arithmetic number, because the mean of its divisors is an integer number (71524503).

Almost surely, 2^285905021 is an apocalyptic number.

It is an amenable number.

285905021 is a deficient number, since it is larger than the sum of its proper divisors (192991).

285905021 is a wasteful number, since it uses less digits than its factorization.

285905021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192990.

The product of its (nonzero) digits is 7200, while the sum is 32.

The square root of 285905021 is about 16908.7261791065. The cubic root of 285905021 is about 658.7802855540.

The spelling of 285905021 in words is "two hundred eighty-five million, nine hundred five thousand, twenty-one".