181722671621 has 2 divisors, whose sum is σ = 181722671622. Its totient is φ = 181722671620.

The previous prime is 181722671597. The next prime is 181722671729. The reversal of 181722671621 is 126176227181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 107433172900 + 74289498721 = 327770^2 + 272561^2 .

It is an emirp because it is prime and its reverse (126176227181) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-181722671621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181722671021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90861335810 + 90861335811.

It is an arithmetic number, because the mean of its divisors is an integer number (90861335811).

Almost surely, 2^181722671621 is an apocalyptic number.

It is an amenable number.

181722671621 is a deficient number, since it is larger than the sum of its proper divisors (1).

181722671621 is an equidigital number, since it uses as much as digits as its factorization.

181722671621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 112896, while the sum is 44.

The spelling of 181722671621 in words is "one hundred eighty-one billion, seven hundred twenty-two million, six hundred seventy-one thousand, six hundred twenty-one".