243987551 has 4 divisors (see below), whose sum is σ = 244305600. Its totient is φ = 243669504.

The previous prime is 243987521. The next prime is 243987559. The reversal of 243987551 is 155789342.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 155789342 = 2 ⋅77894671.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-243987551 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 (243987559) 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 3 ways as a sum of consecutive naturals, for example, 157871 + ... + 159408.

It is an arithmetic number, because the mean of its divisors is an integer number (61076400).

Almost surely, 2^243987551 is an apocalyptic number.

243987551 is a deficient number, since it is larger than the sum of its proper divisors (318049).

243987551 is an equidigital number, since it uses as much as digits as its factorization.

243987551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 318048.

The product of its digits is 302400, while the sum is 44.

The square root of 243987551 is about 15620.1008639509. The cubic root of 243987551 is about 624.8693495440.

The spelling of 243987551 in words is "two hundred forty-three million, nine hundred eighty-seven thousand, five hundred fifty-one".