1781216840 has 64 divisors (see below), whose sum is σ = 4320691200. Its totient is φ = 656969472.

The previous prime is 1781216809. The next prime is 1781216849. The reversal of 1781216840 is 486121871.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 1781216794 and 1781216803.

It is not an unprimeable number, because it can be changed into a prime (1781216849) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 947021 + ... + 948899.

It is an arithmetic number, because the mean of its divisors is an integer number (67510800).

Almost surely, 2^1781216840 is an apocalyptic number.

1781216840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1781216840 is an abundant number, since it is smaller than the sum of its proper divisors (2539474360).

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

1781216840 is a wasteful number, since it uses less digits than its factorization.

1781216840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3726 (or 3722 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 38.

The square root of 1781216840 is about 42204.4646927313. The cubic root of 1781216840 is about 1212.1943742397.

The spelling of 1781216840 in words is "one billion, seven hundred eighty-one million, two hundred sixteen thousand, eight hundred forty".