1978205717 has 4 divisors (see below), whose sum is σ = 1993306656. Its totient is φ = 1963104780.

The previous prime is 1978205699. The next prime is 1978205773. The reversal of 1978205717 is 7175028791.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1978205717 - 2¹⁶ = 1978140181 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978205617) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7550273 + ... + 7550534.

It is an arithmetic number, because the mean of its divisors is an integer number (498326664).

Almost surely, 2^1978205717 is an apocalyptic number.

It is an amenable number.

1978205717 is a deficient number, since it is larger than the sum of its proper divisors (15100939).

1978205717 is a wasteful number, since it uses less digits than its factorization.

1978205717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15100938.

The product of its (nonzero) digits is 246960, while the sum is 47.

The square root of 1978205717 is about 44477.0245969759. The cubic root of 1978205717 is about 1255.3278122304.

The spelling of 1978205717 in words is "one billion, nine hundred seventy-eight million, two hundred five thousand, seven hundred seventeen".