642661379 has 2 divisors, whose sum is σ = 642661380. Its totient is φ = 642661378.

The previous prime is 642661321. The next prime is 642661381. The reversal of 642661379 is 973166246.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642661379 is a prime.

Together with 642661381, 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 (642661309) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321330689 + 321330690.

It is an arithmetic number, because the mean of its divisors is an integer number (321330690).

Almost surely, 2^642661379 is an apocalyptic number.

642661379 is a deficient number, since it is larger than the sum of its proper divisors (1).

642661379 is an equidigital number, since it uses as much as digits as its factorization.

642661379 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 44.

The square root of 642661379 is about 25350.7668325832. The cubic root of 642661379 is about 862.9667588829.

The spelling of 642661379 in words is "six hundred forty-two million, six hundred sixty-one thousand, three hundred seventy-nine".