1665399081 has 16 divisors (see below), whose sum is σ = 2340937728. Its totient is φ = 1051587600.

The previous prime is 1665399053. The next prime is 1665399089. The reversal of 1665399081 is 1809935661.

1665399081 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 1665399081 - 2⁶ = 1665399017 is a prime.

It is a super-2 number, since 2×1665399081² = 5547108197991289122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1665399081.

It is not an unprimeable number, because it can be changed into a prime (1665399089) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 186135 + ... + 194876.

It is an arithmetic number, because the mean of its divisors is an integer number (146308608).

Almost surely, 2^1665399081 is an apocalyptic number.

It is an amenable number.

1665399081 is a deficient number, since it is larger than the sum of its proper divisors (675538647).

1665399081 is a wasteful number, since it uses less digits than its factorization.

1665399081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 381092.

The product of its (nonzero) digits is 349920, while the sum is 48.

The square root of 1665399081 is about 40809.3014029890. The cubic root of 1665399081 is about 1185.3304474648.

The spelling of 1665399081 in words is "one billion, six hundred sixty-five million, three hundred ninety-nine thousand, eighty-one".