1661856943 has 4 divisors (see below), whose sum is σ = 1671141240. Its totient is φ = 1652572648.

The previous prime is 1661856941. The next prime is 1661856971. The reversal of 1661856943 is 3496581661.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1661856943 - 2¹ = 1661856941 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661856941) 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, 4641880 + ... + 4642237.

It is an arithmetic number, because the mean of its divisors is an integer number (417785310).

Almost surely, 2^1661856943 is an apocalyptic number.

1661856943 is a deficient number, since it is larger than the sum of its proper divisors (9284297).

1661856943 is an equidigital number, since it uses as much as digits as its factorization.

1661856943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9284296.

The product of its digits is 933120, while the sum is 49.

The square root of 1661856943 is about 40765.8796421713. The cubic root of 1661856943 is about 1184.4894910315.

The spelling of 1661856943 in words is "one billion, six hundred sixty-one million, eight hundred fifty-six thousand, nine hundred forty-three".