181635661 has 2 divisors, whose sum is σ = 181635662. Its totient is φ = 181635660.

The previous prime is 181635647. The next prime is 181635677. The reversal of 181635661 is 166536181.

181635661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 150062500 + 31573161 = 12250^2 + 5619^2 .

It is a cyclic number.

It is not a de Polignac number, because 181635661 - 2¹³ = 181627469 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 181635661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181635631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90817830 + 90817831.

It is an arithmetic number, because the mean of its divisors is an integer number (90817831).

Almost surely, 2^181635661 is an apocalyptic number.

It is an amenable number.

181635661 is a deficient number, since it is larger than the sum of its proper divisors (1).

181635661 is an equidigital number, since it uses as much as digits as its factorization.

181635661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 37.

The square root of 181635661 is about 13477.2274967814. The cubic root of 181635661 is about 566.3267029278.

The spelling of 181635661 in words is "one hundred eighty-one million, six hundred thirty-five thousand, six hundred sixty-one".