3967664847721 has 2 divisors, whose sum is σ = 3967664847722. Its totient is φ = 3967664847720.

The previous prime is 3967664847691. The next prime is 3967664847733. The reversal of 3967664847721 is 1277484667693.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3729008172096 + 238656675625 = 1931064^2 + 488525^2 .

It is a cyclic number.

It is not a de Polignac number, because 3967664847721 - 2²⁹ = 3967127976809 is a prime.

It is a super-2 number, since 2×3967664847721² (a number of 26 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (3967664842721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1983832423860 + 1983832423861.

It is an arithmetic number, because the mean of its divisors is an integer number (1983832423861).

Almost surely, 2^{3967664847721} is an apocalyptic number.

It is an amenable number.

3967664847721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3967664847721 is an equidigital number, since it uses as much as digits as its factorization.

3967664847721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 512096256, while the sum is 70.

The spelling of 3967664847721 in words is "three trillion, nine hundred sixty-seven billion, six hundred sixty-four million, eight hundred forty-seven thousand, seven hundred twenty-one".