1643455681 has 16 divisors (see below), whose sum is σ = 1890791424. Its totient is φ = 1399293504.

The previous prime is 1643455621. The next prime is 1643455691. The reversal of 1643455681 is 1865543461.

It is not a de Polignac number, because 1643455681 - 2⁹ = 1643455169 is a prime.

It is a super-2 number, since 2×1643455681² = 5401893150822347522, which contains 22 as substring.

It is a Duffinian number.

Its product of digits (345600) is a multiple of the sum of its prime divisors (2880).

It is not an unprimeable number, because it can be changed into a prime (1643455601) 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, 741531 + ... + 743743.

It is an arithmetic number, because the mean of its divisors is an integer number (118174464).

Almost surely, 2^1643455681 is an apocalyptic number.

It is an amenable number.

1643455681 is a deficient number, since it is larger than the sum of its proper divisors (247335743).

1643455681 is a wasteful number, since it uses less digits than its factorization.

1643455681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2880.

The product of its digits is 345600, while the sum is 43.

The square root of 1643455681 is about 40539.5569906727. The cubic root of 1643455681 is about 1180.1014183155.

The spelling of 1643455681 in words is "one billion, six hundred forty-three million, four hundred fifty-five thousand, six hundred eighty-one".