249840781 has 4 divisors (see below), whose sum is σ = 254554812. Its totient is φ = 245126752.

The previous prime is 249840769. The next prime is 249840809. The reversal of 249840781 is 187048942.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 187048942 = 2 ⋅93524471.

It can be written as a sum of positive squares in 2 ways, for example, as 97713225 + 152127556 = 9885^2 + 12334^2 .

It is a cyclic number.

It is not a de Polignac number, because 249840781 - 2¹⁷ = 249709709 is a prime.

It is a super-2 number, since 2×249840781² = 124840831701379922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (249840181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2356936 + ... + 2357041.

It is an arithmetic number, because the mean of its divisors is an integer number (63638703).

Almost surely, 2^249840781 is an apocalyptic number.

It is an amenable number.

249840781 is a deficient number, since it is larger than the sum of its proper divisors (4714031).

249840781 is an equidigital number, since it uses as much as digits as its factorization.

249840781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4714030.

The product of its (nonzero) digits is 129024, while the sum is 43.

The square root of 249840781 is about 15806.3525520596. The cubic root of 249840781 is about 629.8267609666.

The spelling of 249840781 in words is "two hundred forty-nine million, eight hundred forty thousand, seven hundred eighty-one".