1640821 has 24 divisors (see below), whose sum is σ = 2166720. Its totient is φ = 1213056.

The previous prime is 1640819. The next prime is 1640833. The reversal of 1640821 is 1280461.

It is not a de Polignac number, because 1640821 - 2¹ = 1640819 is a prime.

It is a Duffinian number.

1640821 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 1640792 and 1640801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640851) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 22441 + ... + 22513.

It is an arithmetic number, because the mean of its divisors is an integer number (90280).

2^1640821 is an apocalyptic number.

It is an amenable number.

1640821 is a deficient number, since it is larger than the sum of its proper divisors (525899).

1640821 is a wasteful number, since it uses less digits than its factorization.

1640821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125 (or 112 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 1640821 is about 1280.9453540257. The cubic root of 1640821 is about 117.9470460473.

The spelling of 1640821 in words is "one million, six hundred forty thousand, eight hundred twenty-one".