1643881 has 2 divisors, whose sum is σ = 1643882. Its totient is φ = 1643880.

The previous prime is 1643869. The next prime is 1643891. The reversal of 1643881 is 1883461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1166400 + 477481 = 1080^2 + 691^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643881 - 2¹¹ = 1641833 is a prime.

It is a super-2 number, since 2×1643881² = 5404689484322, which contains 22 as substring.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (1643801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821940 + 821941.

It is an arithmetic number, because the mean of its divisors is an integer number (821941).

2^1643881 is an apocalyptic number.

It is an amenable number.

1643881 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643881 is an equidigital number, since it uses as much as digits as its factorization.

1643881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 31.

The square root of 1643881 is about 1282.1392280092. The cubic root of 1643881 is about 118.0203211196.

The spelling of 1643881 in words is "one million, six hundred forty-three thousand, eight hundred eighty-one".