18781940 has 48 divisors (see below), whose sum is σ = 42919632. Its totient is φ = 6875136.

The previous prime is 18781921. The next prime is 18781967. The reversal of 18781940 is 4918781.

It can be written as a sum of positive squares in 8 ways, for example, as 4553956 + 14227984 = 2134^2 + 3772^2 .

It is a super-2 number, since 2×18781940² = 705522540327200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 18781894 and 18781903.

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, 11834 + ... + 13326.

It is an arithmetic number, because the mean of its divisors is an integer number (894159).

Almost surely, 2^18781940 is an apocalyptic number.

18781940 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 18781940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21459816).

18781940 is an abundant number, since it is smaller than the sum of its proper divisors (24137692).

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

18781940 is a wasteful number, since it uses less digits than its factorization.

18781940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1556 (or 1554 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 38.

The square root of 18781940 is about 4333.8135631335. The cubic root of 18781940 is about 265.8154070080.

The spelling of 18781940 in words is "eighteen million, seven hundred eighty-one thousand, nine hundred forty".