661556243 has 2 divisors, whose sum is σ = 661556244. Its totient is φ = 661556242.

The previous prime is 661556239. The next prime is 661556251. The reversal of 661556243 is 342655166.

It is a happy number.

661556243 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661556243 - 2² = 661556239 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 661556197 and 661556206.

It is not a weakly prime, because it can be changed into another prime (661550243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330778121 + 330778122.

It is an arithmetic number, because the mean of its divisors is an integer number (330778122).

Almost surely, 2^661556243 is an apocalyptic number.

661556243 is a deficient number, since it is larger than the sum of its proper divisors (1).

661556243 is an equidigital number, since it uses as much as digits as its factorization.

661556243 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 129600, while the sum is 38.

The square root of 661556243 is about 25720.7356621073. The cubic root of 661556243 is about 871.3425534796.

The spelling of 661556243 in words is "six hundred sixty-one million, five hundred fifty-six thousand, two hundred forty-three".