1681987273 has 4 divisors (see below), whose sum is σ = 1685784528. Its totient is φ = 1678190020.

The previous prime is 1681987271. The next prime is 1681987297. The reversal of 1681987273 is 3727891861.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 3727891861 = 25031 ⋅148931.

It is a cyclic number.

It is not a de Polignac number, because 1681987273 - 2¹ = 1681987271 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1681987273.

It is not an unprimeable number, because it can be changed into a prime (1681987271) 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, 1897963 + ... + 1898848.

It is an arithmetic number, because the mean of its divisors is an integer number (421446132).

Almost surely, 2^1681987273 is an apocalyptic number.

It is an amenable number.

1681987273 is a deficient number, since it is larger than the sum of its proper divisors (3797255).

1681987273 is an equidigital number, since it uses as much as digits as its factorization.

1681987273 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3797254.

The product of its digits is 1016064, while the sum is 52.

The square root of 1681987273 is about 41012.0381473538. The cubic root of 1681987273 is about 1189.2529437716.

The spelling of 1681987273 in words is "one billion, six hundred eighty-one million, nine hundred eighty-seven thousand, two hundred seventy-three".