17991940 has 24 divisors (see below), whose sum is σ = 38021760. Its totient is φ = 7151328.

The previous prime is 17991923. The next prime is 17991949. The reversal of 17991940 is 4919971.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 17991893 and 17991902.

It is not an unprimeable number, because it can be changed into a prime (17991949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 501 + ... + 6019.

It is an arithmetic number, because the mean of its divisors is an integer number (1584240).

Almost surely, 2^17991940 is an apocalyptic number.

17991940 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

17991940 is an abundant number, since it is smaller than the sum of its proper divisors (20029820).

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

17991940 is a wasteful number, since it uses less digits than its factorization.

17991940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5691 (or 5689 counting only the distinct ones).

The product of its (nonzero) digits is 20412, while the sum is 40.

The square root of 17991940 is about 4241.6907006523. The cubic root of 17991940 is about 262.0350165889.

The spelling of 17991940 in words is "seventeen million, nine hundred ninety-one thousand, nine hundred forty".