18999981000 has 2048 divisors, whose sum is σ = 95606784000. Its totient is φ = 3359232000.

The previous prime is 18999980977. The next prime is 18999981017. The reversal of 18999981000 is 18999981.

It is a harmonic number, since the harmonic mean of its divisors is an integer.

It is a super-2 number, since 2×18999981000² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 511 ways as a sum of consecutive naturals, for example, 513512982 + ... + 513513018.

It is an arithmetic number, because the mean of its divisors is an integer number (46683000).

Almost surely, 2^18999981000 is an apocalyptic number.

18999981000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18999981000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47803392000).

18999981000 is an abundant number, since it is smaller than the sum of its proper divisors (76606803000).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18999981000 is a wasteful number, since it uses less digits than its factorization.

18999981000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117 (or 97 counting only the distinct ones).

The product of its (nonzero) digits is 419904, while the sum is 54.

18999981000 divided by its reverse (18999981) gives a cube (1000 = 10³).

It can be divided in two parts, 18999 and 981000, that added together give a palindrome (999999).

The spelling of 18999981000 in words is "eighteen billion, nine hundred ninety-nine million, nine hundred eighty-one thousand".