684537021 has 16 divisors (see below), whose sum is σ = 1159004800. Its totient is φ = 391163904.

The previous prime is 684537013. The next prime is 684537047. The reversal of 684537021 is 120735486.

It is not a de Polignac number, because 684537021 - 2³ = 684537013 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (684537001) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1810756 + ... + 1811133.

It is an arithmetic number, because the mean of its divisors is an integer number (72437800).

Almost surely, 2^684537021 is an apocalyptic number.

It is an amenable number.

684537021 is a deficient number, since it is larger than the sum of its proper divisors (474467779).

684537021 is a wasteful number, since it uses less digits than its factorization.

684537021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3621905 (or 3621899 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 36.

The square root of 684537021 is about 26163.6584024482. The cubic root of 684537021 is about 881.3173370004.

The spelling of 684537021 in words is "six hundred eighty-four million, five hundred thirty-seven thousand, twenty-one".