1661105999 has 4 divisors (see below), whose sum is σ = 1898406864. Its totient is φ = 1423805136.

The previous prime is 1661105983. The next prime is 1661106011. The reversal of 1661105999 is 9995011661.

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

It is a cyclic number.

It is not a de Polignac number, because 1661105999 - 2⁴ = 1661105983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661105909) 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, 118650422 + ... + 118650435.

It is an arithmetic number, because the mean of its divisors is an integer number (474601716).

Almost surely, 2^1661105999 is an apocalyptic number.

1661105999 is a deficient number, since it is larger than the sum of its proper divisors (237300865).

1661105999 is an equidigital number, since it uses as much as digits as its factorization.

1661105999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 237300864.

The product of its (nonzero) digits is 131220, while the sum is 47.

The square root of 1661105999 is about 40756.6681538126. The cubic root of 1661105999 is about 1184.3110522292.

The spelling of 1661105999 in words is "one billion, six hundred sixty-one million, one hundred five thousand, nine hundred ninety-nine".