181395661 has 4 divisors (see below), whose sum is σ = 192066012. Its totient is φ = 170725312.

The previous prime is 181395649. The next prime is 181395673. The reversal of 181395661 is 166593181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166593181 = 1559 ⋅106859.

It is an interprime number because it is at equal distance from previous prime (181395649) and next prime (181395673).

It can be written as a sum of positive squares in 2 ways, for example, as 105966436 + 75429225 = 10294^2 + 8685^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-181395661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181395631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5335150 + ... + 5335183.

It is an arithmetic number, because the mean of its divisors is an integer number (48016503).

Almost surely, 2^181395661 is an apocalyptic number.

It is an amenable number.

181395661 is a deficient number, since it is larger than the sum of its proper divisors (10670351).

181395661 is a wasteful number, since it uses less digits than its factorization.

181395661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10670350.

The product of its digits is 38880, while the sum is 40.

The square root of 181395661 is about 13468.3206451287. The cubic root of 181395661 is about 566.0771588384.

The spelling of 181395661 in words is "one hundred eighty-one million, three hundred ninety-five thousand, six hundred sixty-one".