685661261 has 2 divisors, whose sum is σ = 685661262. Its totient is φ = 685661260.

The previous prime is 685661231. The next prime is 685661279. The reversal of 685661261 is 162166586.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 492618025 + 193043236 = 22195^2 + 13894^2 .

It is a cyclic number.

It is not a de Polignac number, because 685661261 - 2¹⁰ = 685660237 is a prime.

It is a super-2 number, since 2×685661261² = 940262729672220242, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685661231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342830630 + 342830631.

It is an arithmetic number, because the mean of its divisors is an integer number (342830631).

Almost surely, 2^685661261 is an apocalyptic number.

It is an amenable number.

685661261 is a deficient number, since it is larger than the sum of its proper divisors (1).

685661261 is an equidigital number, since it uses as much as digits as its factorization.

685661261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 41.

The square root of 685661261 is about 26185.1343513834. The cubic root of 685661261 is about 881.7995462656.

The spelling of 685661261 in words is "six hundred eighty-five million, six hundred sixty-one thousand, two hundred sixty-one".