249640821 has 12 divisors (see below), whose sum is σ = 361115820. Its totient is φ = 166185600.

The previous prime is 249640819. The next prime is 249640823. The reversal of 249640821 is 128046942.

249640821 is a `hidden beast` number, since 2 + 4 + 9 + 640 + 8 + 2 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (249640819) and next prime (249640823).

It can be written as a sum of positive squares in 2 ways, for example, as 187388721 + 62252100 = 13689^2 + 7890^2 .

It is not a de Polignac number, because 249640821 - 2¹ = 249640819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (249640823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13476 + ... + 26093.

It is an arithmetic number, because the mean of its divisors is an integer number (30092985).

Almost surely, 2^249640821 is an apocalyptic number.

It is an amenable number.

249640821 is a deficient number, since it is larger than the sum of its proper divisors (111474999).

249640821 is a wasteful number, since it uses less digits than its factorization.

249640821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40276 (or 40273 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 249640821 is about 15800.0259809913. The cubic root of 249640821 is about 629.6586888952.

The spelling of 249640821 in words is "two hundred forty-nine million, six hundred forty thousand, eight hundred twenty-one".