3978721693 has 4 divisors (see below), whose sum is σ = 3988744060. Its totient is φ = 3968699328.

The previous prime is 3978721687. The next prime is 3978721709. The reversal of 3978721693 is 3961278793.

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: 3961278793 = 37 ⋅107061589.

It can be written as a sum of positive squares in 2 ways, for example, as 2851239609 + 1127482084 = 53397^2 + 33578^2 .

It is a cyclic number.

It is not a de Polignac number, because 3978721693 - 2⁹ = 3978721181 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 (3978721093) 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 3 ways as a sum of consecutive naturals, for example, 5010588 + ... + 5011381.

It is an arithmetic number, because the mean of its divisors is an integer number (997186015).

Almost surely, 2^3978721693 is an apocalyptic number.

It is an amenable number.

3978721693 is a deficient number, since it is larger than the sum of its proper divisors (10022367).

3978721693 is a wasteful number, since it uses less digits than its factorization.

3978721693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10022366.

The product of its digits is 3429216, while the sum is 55.

The square root of 3978721693 is about 63077.1091046506. The cubic root of 3978721693 is about 1584.5812787989.

The spelling of 3978721693 in words is "three billion, nine hundred seventy-eight million, seven hundred twenty-one thousand, six hundred ninety-three".