194721661 has 2 divisors, whose sum is σ = 194721662. Its totient is φ = 194721660.

The previous prime is 194721617. The next prime is 194721691. The reversal of 194721661 is 166127491.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 145805625 + 48916036 = 12075^2 + 6994^2 .

It is an emirp because it is prime and its reverse (166127491) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-194721661 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 194721661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (194721691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 97360830 + 97360831.

It is an arithmetic number, because the mean of its divisors is an integer number (97360831).

Almost surely, 2^194721661 is an apocalyptic number.

It is an amenable number.

194721661 is a deficient number, since it is larger than the sum of its proper divisors (1).

194721661 is an equidigital number, since it uses as much as digits as its factorization.

194721661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 37.

The square root of 194721661 is about 13954.2703499681. The cubic root of 194721661 is about 579.6129611649.

The spelling of 194721661 in words is "one hundred ninety-four million, seven hundred twenty-one thousand, six hundred sixty-one".