1681991205 has 8 divisors (see below), whose sum is σ = 2691185952. Its totient is φ = 897061968.

The previous prime is 1681991159. The next prime is 1681991243. The reversal of 1681991205 is 5021991861.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1681991205 - 2¹³ = 1681983013 is a prime.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 56066359 + ... + 56066388.

It is an arithmetic number, because the mean of its divisors is an integer number (336398244).

Almost surely, 2^1681991205 is an apocalyptic number.

1681991205 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1681991205 is a deficient number, since it is larger than the sum of its proper divisors (1009194747).

1681991205 is a wasteful number, since it uses less digits than its factorization.

1681991205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112132755.

The product of its (nonzero) digits is 38880, while the sum is 42.

The square root of 1681991205 is about 41012.0860844703. The cubic root of 1681991205 is about 1189.2538704807.

The spelling of 1681991205 in words is "one billion, six hundred eighty-one million, nine hundred ninety-one thousand, two hundred five".