18691961 has 2 divisors, whose sum is σ = 18691962. Its totient is φ = 18691960.

The previous prime is 18691931. The next prime is 18691963. The reversal of 18691961 is 16919681.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9954025 + 8737936 = 3155^2 + 2956^2 .

It is an emirp because it is prime and its reverse (16919681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18691961 - 2¹⁰ = 18690937 is a prime.

Together with 18691963, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18691963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9345980 + 9345981.

It is an arithmetic number, because the mean of its divisors is an integer number (9345981).

Almost surely, 2^18691961 is an apocalyptic number.

It is an amenable number.

18691961 is a deficient number, since it is larger than the sum of its proper divisors (1).

18691961 is an equidigital number, since it uses as much as digits as its factorization.

18691961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 41.

The square root of 18691961 is about 4323.4200582409. The cubic root of 18691961 is about 265.3902450176.

The spelling of 18691961 in words is "eighteen million, six hundred ninety-one thousand, nine hundred sixty-one".