1680921 has 12 divisors (see below), whose sum is σ = 2648880. Its totient is φ = 1018680.

The previous prime is 1680919. The next prime is 1680929. The reversal of 1680921 is 1290861.

It is not a de Polignac number, because 1680921 - 2¹ = 1680919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1680929) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8391 + ... + 8588.

It is an arithmetic number, because the mean of its divisors is an integer number (220740).

2^1680921 is an apocalyptic number.

1680921 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1680921 is a deficient number, since it is larger than the sum of its proper divisors (967959).

1680921 is a wasteful number, since it uses less digits than its factorization.

1680921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16996 (or 16993 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 1680921 is about 1296.5033744653. The cubic root of 1680921 is about 118.9001587063.

It can be divided in two parts, 1680 and 921, that added together give a square (2601 = 51²).

The spelling of 1680921 in words is "one million, six hundred eighty thousand, nine hundred twenty-one".