684556121 has 2 divisors, whose sum is σ = 684556122. Its totient is φ = 684556120.

The previous prime is 684556069. The next prime is 684556123. The reversal of 684556121 is 121655486.

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., 684554896 + 1225 = 26164^2 + 35^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-684556121 is a prime.

Together with 684556123, 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 (684556123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342278060 + 342278061.

It is an arithmetic number, because the mean of its divisors is an integer number (342278061).

Almost surely, 2^684556121 is an apocalyptic number.

It is an amenable number.

684556121 is a deficient number, since it is larger than the sum of its proper divisors (1).

684556121 is an equidigital number, since it uses as much as digits as its factorization.

684556121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 57600, while the sum is 38.

The square root of 684556121 is about 26164.0234100186. The cubic root of 684556121 is about 881.3255337835.

The spelling of 684556121 in words is "six hundred eighty-four million, five hundred fifty-six thousand, one hundred twenty-one".