18877993 has 2 divisors, whose sum is σ = 18877994. Its totient is φ = 18877992.

The previous prime is 18877981. The next prime is 18877997. The reversal of 18877993 is 39977881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17539344 + 1338649 = 4188^2 + 1157^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18877993 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18877993.

It is not a weakly prime, because it can be changed into another prime (18877997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9438996 + 9438997.

It is an arithmetic number, because the mean of its divisors is an integer number (9438997).

Almost surely, 2^18877993 is an apocalyptic number.

It is an amenable number.

18877993 is a deficient number, since it is larger than the sum of its proper divisors (1).

18877993 is an equidigital number, since it uses as much as digits as its factorization.

18877993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 762048, while the sum is 52.

The square root of 18877993 is about 4344.8812411848. The cubic root of 18877993 is about 266.2677735789.

The spelling of 18877993 in words is "eighteen million, eight hundred seventy-seven thousand, nine hundred ninety-three".