1981187840 has 36 divisors (see below), whose sum is σ = 4745567064. Its totient is φ = 792474624.

The previous prime is 1981187783. The next prime is 1981187861. The reversal of 1981187840 is 487811891.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 772622 + ... + 775181.

Almost surely, 2^1981187840 is an apocalyptic number.

1981187840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1981187840 is an abundant number, since it is smaller than the sum of its proper divisors (2764379224).

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

1981187840 is an equidigital number, since it uses as much as digits as its factorization.

1981187840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1547824 (or 1547810 counting only the distinct ones).

The product of its (nonzero) digits is 129024, while the sum is 47.

The square root of 1981187840 is about 44510.5362807504. The cubic root of 1981187840 is about 1255.9582930692.

The spelling of 1981187840 in words is "one billion, nine hundred eighty-one million, one hundred eighty-seven thousand, eight hundred forty".