685513991 has 2 divisors, whose sum is σ = 685513992. Its totient is φ = 685513990.

The previous prime is 685513903. The next prime is 685513999. The reversal of 685513991 is 199315586.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 685513991 - 2¹⁰ = 685512967 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685513999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342756995 + 342756996.

It is an arithmetic number, because the mean of its divisors is an integer number (342756996).

Almost surely, 2^685513991 is an apocalyptic number.

685513991 is a deficient number, since it is larger than the sum of its proper divisors (1).

685513991 is an equidigital number, since it uses as much as digits as its factorization.

685513991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 291600, while the sum is 47.

The square root of 685513991 is about 26182.3221086289. The cubic root of 685513991 is about 881.7364092010.

The spelling of 685513991 in words is "six hundred eighty-five million, five hundred thirteen thousand, nine hundred ninety-one".