1646921 has 2 divisors, whose sum is σ = 1646922. Its totient is φ = 1646920.

The previous prime is 1646903. The next prime is 1646923. The reversal of 1646921 is 1296461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1210000 + 436921 = 1100^2 + 661^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1646921 is a prime.

Together with 1646923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1646923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 823460 + 823461.

It is an arithmetic number, because the mean of its divisors is an integer number (823461).

2^1646921 is an apocalyptic number.

It is an amenable number.

1646921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1646921 is an equidigital number, since it uses as much as digits as its factorization.

1646921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 29.

The square root of 1646921 is about 1283.3241991017. The cubic root of 1646921 is about 118.0930272827.

The spelling of 1646921 in words is "one million, six hundred forty-six thousand, nine hundred twenty-one".