1681215644689 has 27 divisors (see below), whose sum is σ = 2064260593467. Its totient is φ = 1365057631728.

The previous prime is 1681215644663. The next prime is 1681215644737. The reversal of 1681215644689 is 9864465121861.

The square root of 1681215644689 is 1296617.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 242031529089 + 1439184115600 = 491967^2 + 1199660^2 .

It is not a de Polignac number, because 1681215644689 - 2¹¹ = 1681215642641 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1681215644629) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 172445187 + ... + 172454935.

Almost surely, 2^{1681215644689} is an apocalyptic number.

1681215644689 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

1681215644689 is the 1296617-th square number.

1681215644689 is the 648309-th centered octagonal number.

It is an amenable number.

1681215644689 is a deficient number, since it is larger than the sum of its proper divisors (383044948778).

1681215644689 is an frugal number, since it uses more digits than its factorization.

1681215644689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19550 (or 9775 counting only the distinct ones).

The product of its digits is 19906560, while the sum is 61.

The spelling of 1681215644689 in words is "one trillion, six hundred eighty-one billion, two hundred fifteen million, six hundred forty-four thousand, six hundred eighty-nine".