1665409855 has 4 divisors (see below), whose sum is σ = 1998491832. Its totient is φ = 1332327880.

The previous prime is 1665409847. The next prime is 1665409871. The reversal of 1665409855 is 5589045661.

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

It is not a de Polignac number, because 1665409855 - 2³ = 1665409847 is a prime.

It is a super-2 number, since 2×1665409855² = 5547179970262242050, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1665409799 and 1665409808.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166540981 + ... + 166540990.

It is an arithmetic number, because the mean of its divisors is an integer number (499622958).

Almost surely, 2^1665409855 is an apocalyptic number.

1665409855 is a deficient number, since it is larger than the sum of its proper divisors (333081977).

1665409855 is an equidigital number, since it uses as much as digits as its factorization.

1665409855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333081976.

The product of its (nonzero) digits is 1296000, while the sum is 49.

The square root of 1665409855 is about 40809.4334069955. The cubic root of 1665409855 is about 1185.3330035534. Note that the first 3 decimals are identical.

The spelling of 1665409855 in words is "one billion, six hundred sixty-five million, four hundred nine thousand, eight hundred fifty-five".