684928921 has 2 divisors, whose sum is σ = 684928922. Its totient is φ = 684928920.

The previous prime is 684928889. The next prime is 684928927. The reversal of 684928921 is 129829486.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 627001600 + 57927321 = 25040^2 + 7611^2 .

It is a cyclic number.

It is not a de Polignac number, because 684928921 - 2⁵ = 684928889 is a prime.

It is not a weakly prime, because it can be changed into another prime (684928927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342464460 + 342464461.

It is an arithmetic number, because the mean of its divisors is an integer number (342464461).

Almost surely, 2^684928921 is an apocalyptic number.

It is an amenable number.

684928921 is a deficient number, since it is larger than the sum of its proper divisors (1).

684928921 is an equidigital number, since it uses as much as digits as its factorization.

684928921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 497664, while the sum is 49.

The square root of 684928921 is about 26171.1467268823. The cubic root of 684928921 is about 881.4854907367.

The spelling of 684928921 in words is "six hundred eighty-four million, nine hundred twenty-eight thousand, nine hundred twenty-one".