1643491 has 2 divisors, whose sum is σ = 1643492. Its totient is φ = 1643490.

The previous prime is 1643461. The next prime is 1643497. The reversal of 1643491 is 1943461.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1643491 - 2⁷ = 1643363 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1643497) 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 as a sum of consecutive naturals, namely, 821745 + 821746.

It is an arithmetic number, because the mean of its divisors is an integer number (821746).

2^1643491 is an apocalyptic number.

1643491 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643491 is an equidigital number, since it uses as much as digits as its factorization.

1643491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2592, while the sum is 28.

The square root of 1643491 is about 1281.9871294206. The cubic root of 1643491 is about 118.0109871987.

It can be divided in two parts, 164 and 3491, that added together give a triangular number (3655 = T₈₅).

The spelling of 1643491 in words is "one million, six hundred forty-three thousand, four hundred ninety-one".