1661551543 has 2 divisors, whose sum is σ = 1661551544. Its totient is φ = 1661551542.

The previous prime is 1661551523. The next prime is 1661551601. The reversal of 1661551543 is 3451551661.

It is a weak prime.

It is an emirp because it is prime and its reverse (3451551661) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661551543 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661551513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830775771 + 830775772.

It is an arithmetic number, because the mean of its divisors is an integer number (830775772).

Almost surely, 2^1661551543 is an apocalyptic number.

1661551543 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661551543 is an equidigital number, since it uses as much as digits as its factorization.

1661551543 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54000, while the sum is 37.

The square root of 1661551543 is about 40762.1336904731. The cubic root of 1661551543 is about 1184.4169285779.

The spelling of 1661551543 in words is "one billion, six hundred sixty-one million, five hundred fifty-one thousand, five hundred forty-three".