18991840 has 96 divisors (see below), whose sum is σ = 53028864. Its totient is φ = 6289920.

The previous prime is 18991831. The next prime is 18991867. The reversal of 18991840 is 4819981.

18991840 = T₅₁ + T₅₂ + ... + T₄₈₄.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 18991793 and 18991802.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34447 + ... + 34993.

It is an arithmetic number, because the mean of its divisors is an integer number (552384).

Almost surely, 2^18991840 is an apocalyptic number.

18991840 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 18991840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26514432).

18991840 is an abundant number, since it is smaller than the sum of its proper divisors (34037024).

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

18991840 is a wasteful number, since it uses less digits than its factorization.

18991840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 600 (or 592 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 40.

The square root of 18991840 is about 4357.9628268263. The cubic root of 18991840 is about 266.8019591260.

It can be divided in two parts, 189 and 91840, that added together give a palindrome (92029).

The spelling of 18991840 in words is "eighteen million, nine hundred ninety-one thousand, eight hundred forty".