1985665181 has 2 divisors, whose sum is σ = 1985665182. Its totient is φ = 1985665180.

The previous prime is 1985665159. The next prime is 1985665249. The reversal of 1985665181 is 1815665891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1724325625 + 261339556 = 41525^2 + 16166^2 .

It is a cyclic number.

It is not a de Polignac number, because 1985665181 - 2⁶ = 1985665117 is a prime.

It is a super-2 number, since 2×1985665181² = 7885732422071525522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1985665081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 992832590 + 992832591.

It is an arithmetic number, because the mean of its divisors is an integer number (992832591).

Almost surely, 2^1985665181 is an apocalyptic number.

It is an amenable number.

1985665181 is a deficient number, since it is larger than the sum of its proper divisors (1).

1985665181 is an equidigital number, since it uses as much as digits as its factorization.

1985665181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 518400, while the sum is 50.

The square root of 1985665181 is about 44560.8031906966. The cubic root of 1985665181 is about 1256.9037061581.

The spelling of 1985665181 in words is "one billion, nine hundred eighty-five million, six hundred sixty-five thousand, one hundred eighty-one".