1781661616 has 80 divisors (see below), whose sum is σ = 4163304960. Its totient is φ = 721543680.

The previous prime is 1781661599. The next prime is 1781661617. The reversal of 1781661616 is 6161661871.

It is a super-2 number, since 2×1781661616² = 6348636227855462912, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1781661617) 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, 1107885 + ... + 1109491.

It is an arithmetic number, because the mean of its divisors is an integer number (52041312).

Almost surely, 2^1781661616 is an apocalyptic number.

1781661616 is a gapful number since it is divisible by the number (16) 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 1781661616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2081652480).

1781661616 is an abundant number, since it is smaller than the sum of its proper divisors (2381643344).

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

1781661616 is a wasteful number, since it uses less digits than its factorization.

1781661616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2162 (or 2156 counting only the distinct ones).

The product of its digits is 72576, while the sum is 43.

The square root of 1781661616 is about 42209.7336641680. The cubic root of 1781661616 is about 1212.2952622175.

The spelling of 1781661616 in words is "one billion, seven hundred eighty-one million, six hundred sixty-one thousand, six hundred sixteen".