1643640 has 32 divisors (see below), whose sum is σ = 4931280. Its totient is φ = 438272.

The previous prime is 1643639. The next prime is 1643641. The reversal of 1643640 is 463461.

It is an interprime number because it is at equal distance from previous prime (1643639) and next prime (1643641).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 1643640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1643641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6729 + ... + 6968.

2^1643640 is an apocalyptic number.

1643640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1643640 is an abundant number, since it is smaller than the sum of its proper divisors (3287640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1643640 is a wasteful number, since it uses less digits than its factorization.

1643640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13711 (or 13707 counting only the distinct ones).

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

The square root of 1643640 is about 1282.0452410114. The cubic root of 1643640 is about 118.0145534094.

The spelling of 1643640 in words is "one million, six hundred forty-three thousand, six hundred forty".