1640021 has 2 divisors, whose sum is σ = 1640022. Its totient is φ = 1640020.

The previous prime is 1640017. The next prime is 1640033. The reversal of 1640021 is 1200461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1060900 + 579121 = 1030^2 + 761^2 .

It is an emirp because it is prime and its reverse (1200461) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1640021 - 2² = 1640017 is a prime.

It is a super-3 number, since 3×1640021³ = 13233340340909187783, which contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1639978 and 1640005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1640071) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 820010 + 820011.

It is an arithmetic number, because the mean of its divisors is an integer number (820011).

2^1640021 is an apocalyptic number.

It is an amenable number.

1640021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1640021 is an equidigital number, since it uses as much as digits as its factorization.

1640021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 1640021 is about 1280.6330465828. The cubic root of 1640021 is about 117.9278741458.

Adding to 1640021 its reverse (1200461), we get a palindrome (2840482).

The spelling of 1640021 in words is "one million, six hundred forty thousand, twenty-one".