1978165639 has 4 divisors (see below), whose sum is σ = 2082279640. Its totient is φ = 1874051640.

The previous prime is 1978165633. The next prime is 1978165649. The reversal of 1978165639 is 9365618791.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9365618791 = 23 ⋅407200817.

It is a cyclic number.

It is not a de Polignac number, because 1978165639 - 2²⁹ = 1441294727 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1978165639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978165633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 52056972 + ... + 52057009.

It is an arithmetic number, because the mean of its divisors is an integer number (520569910).

Almost surely, 2^1978165639 is an apocalyptic number.

1978165639 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

1978165639 is a deficient number, since it is larger than the sum of its proper divisors (104114001).

1978165639 is a wasteful number, since it uses less digits than its factorization.

1978165639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104114000.

The product of its digits is 2449440, while the sum is 55.

The square root of 1978165639 is about 44476.5740474691. The cubic root of 1978165639 is about 1255.3193346207.

The spelling of 1978165639 in words is "one billion, nine hundred seventy-eight million, one hundred sixty-five thousand, six hundred thirty-nine".