661346891 has 2 divisors, whose sum is σ = 661346892. Its totient is φ = 661346890.

The previous prime is 661346857. The next prime is 661346893. The reversal of 661346891 is 198643166.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661346891 is a prime.

It is a Sophie Germain prime.

Together with 661346893, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661346893) 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, 330673445 + 330673446.

It is an arithmetic number, because the mean of its divisors is an integer number (330673446).

Almost surely, 2^661346891 is an apocalyptic number.

661346891 is a deficient number, since it is larger than the sum of its proper divisors (1).

661346891 is an equidigital number, since it uses as much as digits as its factorization.

661346891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 44.

The square root of 661346891 is about 25716.6656275653. The cubic root of 661346891 is about 871.2506305560.

The spelling of 661346891 in words is "six hundred sixty-one million, three hundred forty-six thousand, eight hundred ninety-one".