609781 has 2 divisors, whose sum is σ = 609782. Its totient is φ = 609780.

The previous prime is 609779. The next prime is 609803. The reversal of 609781 is 187906.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 555025 + 54756 = 745^2 + 234^2 .

It is a cyclic number.

It is not a de Polignac number, because 609781 - 2¹ = 609779 is a prime.

It is a super-2 number, since 2×609781² = 743665735922, which contains 22 as substring.

Together with 609779, it forms a pair of twin primes.

609781 is a lucky number.

It is equal to p₄₉₈₄₆ and since 609781 and 49846 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (609701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 304890 + 304891.

It is an arithmetic number, because the mean of its divisors is an integer number (304891).

2⁶⁰⁹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

609781 is a deficient number, since it is larger than the sum of its proper divisors (1).

609781 is an equidigital number, since it uses as much as digits as its factorization.

609781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 609781 is about 780.8847546213. The cubic root of 609781 is about 84.7991103651.

Subtracting from 609781 its reverse (187906), we obtain a cube (421875 = 75³).

The spelling of 609781 in words is "six hundred nine thousand, seven hundred eighty-one".