2181730681 has 9 divisors (see below), whose sum is σ = 2363123469. Its totient is φ = 2013344736.

The previous prime is 2181730673. The next prime is 2181730709. The reversal of 2181730681 is 1860371812.

The square root of 2181730681 is 46709.

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

It can be written as a sum of positive squares in 4 ways, for example, as 649791081 + 1531939600 = 25491^2 + 39140^2 .

It is not a de Polignac number, because 2181730681 - 2³ = 2181730673 is a prime.

It is a super-2 number, since 2×2181730681² = 9519897528833447522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 2181730681.

It is not an unprimeable number, because it can be changed into a prime (2181730181) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 605421 + ... + 609013.

Almost surely, 2^2181730681 is an apocalyptic number.

2181730681 is the 46709-th square number.

2181730681 is the 23355-th centered octagonal number.

It is an amenable number.

2181730681 is a deficient number, since it is larger than the sum of its proper divisors (181392788).

2181730681 is an frugal number, since it uses more digits than its factorization.

2181730681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7212 (or 3606 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 37.

The cubic root of 2181730681 is about 1296.9812957523.

The spelling of 2181730681 in words is "two billion, one hundred eighty-one million, seven hundred thirty thousand, six hundred eighty-one".