3978078721 has 4 divisors (see below), whose sum is σ = 3998272212. Its totient is φ = 3957885232.

The previous prime is 3978078707. The next prime is 3978078749. The reversal of 3978078721 is 1278708793.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3432202225 + 545876496 = 58585^2 + 23364^2 .

It is a cyclic number.

It is not a de Polignac number, because 3978078721 - 2⁷ = 3978078593 is a prime.

It is a super-2 number, since 2×3978078721² = 31650220620945991682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3978078121) 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, 10096450 + ... + 10096843.

It is an arithmetic number, because the mean of its divisors is an integer number (999568053).

Almost surely, 2^3978078721 is an apocalyptic number.

It is an amenable number.

3978078721 is a deficient number, since it is larger than the sum of its proper divisors (20193491).

3978078721 is a wasteful number, since it uses less digits than its factorization.

3978078721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20193490.

The product of its (nonzero) digits is 1185408, while the sum is 52.

The square root of 3978078721 is about 63072.0121844864. The cubic root of 3978078721 is about 1584.4959166851.

The spelling of 3978078721 in words is "three billion, nine hundred seventy-eight million, seventy-eight thousand, seven hundred twenty-one".