18991980 has 72 divisors (see below), whose sum is σ = 65843232. Its totient is φ = 4340736.

The previous prime is 18991969. The next prime is 18991981. The reversal of 18991980 is 8919981.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (18991981) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6277 + ... + 8796.

Almost surely, 2^18991980 is an apocalyptic number.

18991980 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18991980 is an abundant number, since it is smaller than the sum of its proper divisors (46851252).

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

18991980 is a wasteful number, since it uses less digits than its factorization.

18991980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15095 (or 15090 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 45.

The square root of 18991980 is about 4357.9788893477. The cubic root of 18991980 is about 266.8026147090.

The spelling of 18991980 in words is "eighteen million, nine hundred ninety-one thousand, nine hundred eighty".