1978618691 has 8 divisors (see below), whose sum is σ = 2261570304. Its totient is φ = 1695740040.

The previous prime is 1978618673. The next prime is 1978618703. The reversal of 1978618691 is 1968168791.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1978618691 - 2¹⁸ = 1978356547 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1978648691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65546 + ... + 90848.

It is an arithmetic number, because the mean of its divisors is an integer number (282696288).

Almost surely, 2^1978618691 is an apocalyptic number.

1978618691 is a deficient number, since it is larger than the sum of its proper divisors (282951613).

1978618691 is a wasteful number, since it uses less digits than its factorization.

1978618691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36481.

The product of its digits is 1306368, while the sum is 56.

The square root of 1978618691 is about 44481.6669089637. Note that the first 3 decimals coincide. The cubic root of 1978618691 is about 1255.4151610288.

The spelling of 1978618691 in words is "one billion, nine hundred seventy-eight million, six hundred eighteen thousand, six hundred ninety-one".