18939997 has 2 divisors, whose sum is σ = 18939998. Its totient is φ = 18939996.

The previous prime is 18939983. The next prime is 18940007. The reversal of 18939997 is 79993981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11655396 + 7284601 = 3414^2 + 2699^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18939997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18939937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9469998 + 9469999.

It is an arithmetic number, because the mean of its divisors is an integer number (9469999).

Almost surely, 2^18939997 is an apocalyptic number.

It is an amenable number.

18939997 is a deficient number, since it is larger than the sum of its proper divisors (1).

18939997 is an equidigital number, since it uses as much as digits as its factorization.

18939997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1102248, while the sum is 55.

The square root of 18939997 is about 4352.0106847295. The cubic root of 18939997 is about 266.5589702267.

It can be divided in two parts, 189 and 39997, that added together give a triangular number (40186 = T₂₈₃).

The spelling of 18939997 in words is "eighteen million, nine hundred thirty-nine thousand, nine hundred ninety-seven".