1982172809 has 4 divisors (see below), whose sum is σ = 1982775504. Its totient is φ = 1981570116.

The previous prime is 1982172799. The next prime is 1982172833. The reversal of 1982172809 is 9082712891.

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: 9082712891 = 7 ⋅1297530413.

It is a cyclic number.

It is not a de Polignac number, because 1982172809 - 2⁴ = 1982172793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1982172859) 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, 296387 + ... + 303000.

It is an arithmetic number, because the mean of its divisors is an integer number (495693876).

Almost surely, 2^1982172809 is an apocalyptic number.

It is an amenable number.

1982172809 is a deficient number, since it is larger than the sum of its proper divisors (602695).

1982172809 is an equidigital number, since it uses as much as digits as its factorization.

1982172809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 602694.

The product of its (nonzero) digits is 145152, while the sum is 47.

The square root of 1982172809 is about 44521.5993535722. The cubic root of 1982172809 is about 1256.1663963438.

The spelling of 1982172809 in words is "one billion, nine hundred eighty-two million, one hundred seventy-two thousand, eight hundred nine".