18961993 has 2 divisors, whose sum is σ = 18961994. Its totient is φ = 18961992.

The previous prime is 18961961. The next prime is 18962017. The reversal of 18961993 is 39916981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15976009 + 2985984 = 3997^2 + 1728^2 .

It is a cyclic number.

It is not a de Polignac number, because 18961993 - 2⁵ = 18961961 is a prime.

It is not a weakly prime, because it can be changed into another prime (18961933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9480996 + 9480997.

It is an arithmetic number, because the mean of its divisors is an integer number (9480997).

Almost surely, 2^18961993 is an apocalyptic number.

It is an amenable number.

18961993 is a deficient number, since it is larger than the sum of its proper divisors (1).

18961993 is an equidigital number, since it uses as much as digits as its factorization.

18961993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 104976, while the sum is 46.

The square root of 18961993 is about 4354.5370592062. The cubic root of 18961993 is about 266.6621198878.

The spelling of 18961993 in words is "eighteen million, nine hundred sixty-one thousand, nine hundred ninety-three".