1998421553091 has 16 divisors (see below), whose sum is σ = 2670486432768. Its totient is φ = 1329319168800.

The previous prime is 1998421553039. The next prime is 1998421553123. The reversal of 1998421553091 is 1903551248991.

It is not a de Polignac number, because 1998421553091 - 2³⁸ = 1723543646147 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1998421553591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41530956 + ... + 41579046.

It is an arithmetic number, because the mean of its divisors is an integer number (166905402048).

Almost surely, 2^{1998421553091} is an apocalyptic number.

1998421553091 is a deficient number, since it is larger than the sum of its proper divisors (672064879677).

1998421553091 is a wasteful number, since it uses less digits than its factorization.

1998421553091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78602.

The product of its (nonzero) digits is 3499200, while the sum is 57.

The spelling of 1998421553091 in words is "one trillion, nine hundred ninety-eight billion, four hundred twenty-one million, five hundred fifty-three thousand, ninety-one".