1978289391 has 8 divisors (see below), whose sum is σ = 2840620720. Its totient is φ = 1217408832.

The previous prime is 1978289389. The next prime is 1978289429. The reversal of 1978289391 is 1939828791.

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

It is not a de Polignac number, because 1978289391 - 2¹ = 1978289389 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 (1978289311) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25362646 + ... + 25362723.

It is an arithmetic number, because the mean of its divisors is an integer number (355077590).

Almost surely, 2^1978289391 is an apocalyptic number.

1978289391 is a deficient number, since it is larger than the sum of its proper divisors (862331329).

1978289391 is a wasteful number, since it uses less digits than its factorization.

1978289391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50725385.

The product of its digits is 1959552, while the sum is 57.

The square root of 1978289391 is about 44477.9652299878. The cubic root of 1978289391 is about 1255.3455112354.

The spelling of 1978289391 in words is "one billion, nine hundred seventy-eight million, two hundred eighty-nine thousand, three hundred ninety-one".