609991 has 2 divisors, whose sum is σ = 609992. Its totient is φ = 609990.

The previous prime is 609989. The next prime is 609997. The reversal of 609991 is 199906.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 609991 - 2¹ = 609989 is a prime.

Together with 609989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (609997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 304995 + 304996.

It is an arithmetic number, because the mean of its divisors is an integer number (304996).

2⁶⁰⁹⁹⁹¹ is an apocalyptic number.

609991 is a deficient number, since it is larger than the sum of its proper divisors (1).

609991 is an equidigital number, since it uses as much as digits as its factorization.

609991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 609991 is about 781.0192059098. The cubic root of 609991 is about 84.8088437881.

It can be divided in two parts, 609 and 991, that added together give a square (1600 = 40²).

The spelling of 609991 in words is "six hundred nine thousand, nine hundred ninety-one".