181811837681 has 2 divisors, whose sum is σ = 181811837682. Its totient is φ = 181811837680.

The previous prime is 181811837651. The next prime is 181811837723. The reversal of 181811837681 is 186738118181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 141683735281 + 40128102400 = 376409^2 + 200320^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-181811837681 is a prime.

It is a super-2 number, since 2×181811837681² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (181811837621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90905918840 + 90905918841.

It is an arithmetic number, because the mean of its divisors is an integer number (90905918841).

Almost surely, 2^181811837681 is an apocalyptic number.

It is an amenable number.

181811837681 is a deficient number, since it is larger than the sum of its proper divisors (1).

181811837681 is an equidigital number, since it uses as much as digits as its factorization.

181811837681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 516096, while the sum is 53.

The spelling of 181811837681 in words is "one hundred eighty-one billion, eight hundred eleven million, eight hundred thirty-seven thousand, six hundred eighty-one".