661543123 has 2 divisors, whose sum is σ = 661543124. Its totient is φ = 661543122.

The previous prime is 661543097. The next prime is 661543171. The reversal of 661543123 is 321345166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661543123 - 2¹³ = 661534931 is a prime.

It is not a weakly prime, because it can be changed into another prime (661543723) 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 as a sum of consecutive naturals, namely, 330771561 + 330771562.

It is an arithmetic number, because the mean of its divisors is an integer number (330771562).

Almost surely, 2^661543123 is an apocalyptic number.

661543123 is a deficient number, since it is larger than the sum of its proper divisors (1).

661543123 is an equidigital number, since it uses as much as digits as its factorization.

661543123 is an odious number, because the sum of its binary digits is odd.

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

The square root of 661543123 is about 25720.4806137055. The cubic root of 661543123 is about 871.3367932790.

Adding to 661543123 its reverse (321345166), we get a palindrome (982888289).

The spelling of 661543123 in words is "six hundred sixty-one million, five hundred forty-three thousand, one hundred twenty-three".