181722671021 has 2 divisors, whose sum is σ = 181722671022. Its totient is φ = 181722671020.

The previous prime is 181722671003. The next prime is 181722671051. The reversal of 181722671021 is 120176227181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 100226695396 + 81495975625 = 316586^2 + 285475^2 .

It is an emirp because it is prime and its reverse (120176227181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 181722671021 - 2³⁴ = 164542801837 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181722671051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90861335510 + 90861335511.

It is an arithmetic number, because the mean of its divisors is an integer number (90861335511).

Almost surely, 2^181722671021 is an apocalyptic number.

It is an amenable number.

181722671021 is a deficient number, since it is larger than the sum of its proper divisors (1).

181722671021 is an equidigital number, since it uses as much as digits as its factorization.

181722671021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18816, while the sum is 38.

The spelling of 181722671021 in words is "one hundred eighty-one billion, seven hundred twenty-two million, six hundred seventy-one thousand, twenty-one".