249821561 has 12 divisors (see below), whose sum is σ = 286539456. Its totient is φ = 217233720.

The previous prime is 249821527. The next prime is 249821563. The reversal of 249821561 is 165128942.

It is not a de Polignac number, because 249821561 - 2¹⁴ = 249805177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (249821563) 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 11 ways as a sum of consecutive naturals, for example, 42101 + ... + 47666.

It is an arithmetic number, because the mean of its divisors is an integer number (23878288).

Almost surely, 2^249821561 is an apocalyptic number.

It is an amenable number.

249821561 is a deficient number, since it is larger than the sum of its proper divisors (36717895).

249821561 is a wasteful number, since it uses less digits than its factorization.

249821561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89812 (or 89801 counting only the distinct ones).

The product of its digits is 34560, while the sum is 38.

The square root of 249821561 is about 15805.7445569641. The cubic root of 249821561 is about 629.8106099060.

The spelling of 249821561 in words is "two hundred forty-nine million, eight hundred twenty-one thousand, five hundred sixty-one".