1640421 has 12 divisors (see below), whose sum is σ = 2391948. Its totient is φ = 1083264.

The previous prime is 1640399. The next prime is 1640423. The reversal of 1640421 is 1240461.

1640421 = T₃₃₅ + T₃₃₆ + ... + T₃₆₁.

1640421 is a `hidden beast` number, since 1 + 640 + 4 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 408321 + 1232100 = 639^2 + 1110^2 .

It is not a de Polignac number, because 1640421 - 2¹⁴ = 1624037 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1640394 and 1640403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 211 + ... + 1823.

It is an arithmetic number, because the mean of its divisors is an integer number (199329).

2^1640421 is an apocalyptic number.

It is an amenable number.

1640421 is a deficient number, since it is larger than the sum of its proper divisors (751527).

1640421 is a wasteful number, since it uses less digits than its factorization.

1640421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1732 (or 1729 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 1640421 is about 1280.7892098234. The cubic root of 1640421 is about 117.9374608757.

Adding to 1640421 its reverse (1240461), we get a palindrome (2880882).

The spelling of 1640421 in words is "one million, six hundred forty thousand, four hundred twenty-one".