1661782681 has 8 divisors (see below), whose sum is σ = 1803705344. Its totient is φ = 1521873360.

The previous prime is 1661782673. The next prime is 1661782721. The reversal of 1661782681 is 1862871661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1661782681 - 2³ = 1661782673 is a prime.

It is a super-2 number, since 2×1661782681² = 5523043357743095522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661782631) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 501615 + ... + 504916.

It is an arithmetic number, because the mean of its divisors is an integer number (225463168).

Almost surely, 2^1661782681 is an apocalyptic number.

It is an amenable number.

1661782681 is a deficient number, since it is larger than the sum of its proper divisors (141922663).

1661782681 is a wasteful number, since it uses less digits than its factorization.

1661782681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1006671.

The product of its digits is 193536, while the sum is 46.

The square root of 1661782681 is about 40764.9687967500. The cubic root of 1661782681 is about 1184.4718473409.

The spelling of 1661782681 in words is "one billion, six hundred sixty-one million, seven hundred eighty-two thousand, six hundred eighty-one".