1640643 has 4 divisors (see below), whose sum is σ = 2187528. Its totient is φ = 1093760.

The previous prime is 1640641. The next prime is 1640657. The reversal of 1640643 is 3460461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3460461 = 3 ⋅1153487.

It is a cyclic number.

It is not a de Polignac number, because 1640643 - 2¹ = 1640641 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (1640641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273438 + ... + 273443.

It is an arithmetic number, because the mean of its divisors is an integer number (546882).

2^1640643 is an apocalyptic number.

1640643 is a deficient number, since it is larger than the sum of its proper divisors (546885).

1640643 is an equidigital number, since it uses as much as digits as its factorization.

1640643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546884.

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 1640643 is about 1280.8758722062. The cubic root of 1640643 is about 117.9427808384.

The spelling of 1640643 in words is "one million, six hundred forty thousand, six hundred forty-three".