1998665642 has 4 divisors (see below), whose sum is σ = 2997998466. Its totient is φ = 999332820.

The previous prime is 1998665629. The next prime is 1998665657. The reversal of 1998665642 is 2465668991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 2465668991 = 193 ⋅12775487.

It can be written as a sum of positive squares in only one way, i.e., 1957974001 + 40691641 = 44249^2 + 6379^2 .

It is a super-2 number, since 2×1998665642² = 7989328697022544328, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499666409 + ... + 499666412.

Almost surely, 2^1998665642 is an apocalyptic number.

1998665642 is a deficient number, since it is larger than the sum of its proper divisors (999332824).

1998665642 is an equidigital number, since it uses as much as digits as its factorization.

1998665642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 999332823.

The product of its digits is 5598720, while the sum is 56.

The square root of 1998665642 is about 44706.4384848536. The cubic root of 1998665642 is about 1259.6407899357.

The spelling of 1998665642 in words is "one billion, nine hundred ninety-eight million, six hundred sixty-five thousand, six hundred forty-two".