18915817 has 2 divisors, whose sum is σ = 18915818. Its totient is φ = 18915816.

The previous prime is 18915763. The next prime is 18915823. The reversal of 18915817 is 71851981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18800896 + 114921 = 4336^2 + 339^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18915817 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18915817.

It is not a weakly prime, because it can be changed into another prime (18915857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9457908 + 9457909.

It is an arithmetic number, because the mean of its divisors is an integer number (9457909).

Almost surely, 2^18915817 is an apocalyptic number.

It is an amenable number.

18915817 is a deficient number, since it is larger than the sum of its proper divisors (1).

18915817 is an equidigital number, since it uses as much as digits as its factorization.

18915817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20160, while the sum is 40.

The square root of 18915817 is about 4349.2317712442. The cubic root of 18915817 is about 266.4454865636.

The spelling of 18915817 in words is "eighteen million, nine hundred fifteen thousand, eight hundred seventeen".