684668716421 has 2 divisors, whose sum is σ = 684668716422. Its totient is φ = 684668716420.

The previous prime is 684668716393. The next prime is 684668716481. The reversal of 684668716421 is 124617866486.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 494061381025 + 190607335396 = 702895^2 + 436586^2 .

It is a cyclic number.

It is not a de Polignac number, because 684668716421 - 2¹⁸ = 684668454277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (684668716481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342334358210 + 342334358211.

It is an arithmetic number, because the mean of its divisors is an integer number (342334358211).

Almost surely, 2^684668716421 is an apocalyptic number.

It is an amenable number.

684668716421 is a deficient number, since it is larger than the sum of its proper divisors (1).

684668716421 is an equidigital number, since it uses as much as digits as its factorization.

684668716421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18579456, while the sum is 59.

The spelling of 684668716421 in words is "six hundred eighty-four billion, six hundred sixty-eight million, seven hundred sixteen thousand, four hundred twenty-one".