661315243 has 4 divisors (see below), whose sum is σ = 665527600. Its totient is φ = 657102888.

The previous prime is 661315223. The next prime is 661315253. The reversal of 661315243 is 342513166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 342513166 = 2 ⋅171256583.

It is a cyclic number.

It is not a de Polignac number, because 661315243 - 2¹³ = 661307051 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661315223) 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 3 ways as a sum of consecutive naturals, for example, 2105943 + ... + 2106256.

It is an arithmetic number, because the mean of its divisors is an integer number (166381900).

Almost surely, 2^661315243 is an apocalyptic number.

661315243 is a deficient number, since it is larger than the sum of its proper divisors (4212357).

661315243 is a wasteful number, since it uses less digits than its factorization.

661315243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4212356.

The product of its digits is 12960, while the sum is 31.

The square root of 661315243 is about 25716.0502993753. The cubic root of 661315243 is about 871.2367327664.

The spelling of 661315243 in words is "six hundred sixty-one million, three hundred fifteen thousand, two hundred forty-three".