1981391040 has 168 divisors, whose sum is σ = 7035320448. Its totient is φ = 511303680.

The previous prime is 1981391029. The next prime is 1981391047. The reversal of 1981391040 is 401931891.

It is a super-3 number, since 3×1981391040³ (a number of 29 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 1981390986 and 1981391004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981391047) 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, 78184 + ... + 100376.

Almost surely, 2^1981391040 is an apocalyptic number.

1981391040 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 1981391040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3517660224).

1981391040 is an abundant number, since it is smaller than the sum of its proper divisors (5053929408).

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

1981391040 is a wasteful number, since it uses less digits than its factorization.

1981391040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22247 (or 22234 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 1981391040 is about 44512.8188278388. The cubic root of 1981391040 is about 1256.0012306099.

The spelling of 1981391040 in words is "one billion, nine hundred eighty-one million, three hundred ninety-one thousand, forty".