684240921 has 24 divisors (see below), whose sum is σ = 1216429760. Its totient is φ = 360917856.

The previous prime is 684240913. The next prime is 684240937. The reversal of 684240921 is 129042486.

It is not a de Polignac number, because 684240921 - 2³ = 684240913 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (684240941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 416911 + ... + 418548.

Almost surely, 2^684240921 is an apocalyptic number.

It is an amenable number.

684240921 is a deficient number, since it is larger than the sum of its proper divisors (532188839).

684240921 is a wasteful number, since it uses less digits than its factorization.

684240921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 835485 (or 835482 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 684240921 is about 26157.9991780717. Note that the first 3 decimals coincide. The cubic root of 684240921 is about 881.1902458956.

The spelling of 684240921 in words is "six hundred eighty-four million, two hundred forty thousand, nine hundred twenty-one".